/************************************************************************
 * Copyright (C) 2006-2009 Philipp Marek.
 *
 * This program is free software;  you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 ************************************************************************/
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <time.h>

#include <subversion-1/svn_delta.h>
#include <subversion-1/svn_ra.h>

#include "revert.h"
#include "waa.h"
#include "est_ops.h"
#include "racallback.h"
#include "warnings.h"
#include "resolve.h"
#include "checksum.h"
#include "props.h"
#include "helper.h"
#include "url.h"
#include "update.h"
#include "cp_mv.h"
#include "status.h"


/** \file
 * \ref revert action.
 * This reverts local changes, ie. resets the given paths to the repository
 * versions.
 * This cannot be undone by fsvs - keep backups :-) */

/** \addtogroup cmds
 *
 * \section revert
 *
 * \code
 * fsvs revert [-rRev] [-R] PATH [PATH...]
 * \endcode
 * 
 * This command undoes local modifications:
 * - An entry that is marked to be unversioned gets this flag removed.
 * - For a already versioned entry (existing in the repository) the local 
 *   entry is replaced with its repository version, and its status and 
 *   flags are cleared.
 * - An entry that is a \b modified copy destination gets reverted to the 
 *   copy source data.
 * - Manually added entries are changed back to <i>"N"</i>ew.\b
 *
 * Please note that implicitly copied entries, ie. entries that are marked 
 * as copied because some parent directory is the base of a copy, <b>can 
 * not</b> be un-copied; they can only be reverted to their original 
 * (copied-from) data, or removed.
 *
 * If you want to undo a \c copy operation, please see the \ref uncopy 
 * "uncopy" command.
 *
 * See also \ref howto_entry_statii.
 * 
 * If a directory is given on the command line <b>all versioned entries in 
 * this directory</b> are reverted to the old state; this behaviour can be 
 * modified with \ref glob_opt_rec "-R/-N", or see below.
 *
 * The reverted entries are printed, along with the status they had \b 
 * before the revert (because the new status is per definition \e 
 * unchanged).
 *
 * If a revision is given, the entries' data is taken from this revision; 
 * furthermore, the \b new status of that entry is shown.
 *
 * \note Please note that mixed revision working copies are not (yet) 
 * possible; the \e BASE revision is not changed, and a simple \c revert 
 * without a revision arguments gives you that. \n
 * By giving a revision parameter you can just choose to get the text from 
 * a different revision.
 *
 *
 * \subsection rev_cmp_up Difference to update
 * If something doesn't work as it should in the installation you can 
 * revert entries until you are satisfied, and directly \ref commit 
 * "commit" the new state. 
 * 
 * In contrast, if you \ref update "update" to an older version, you 
 * - cannot choose single entries (no mixed revision working copies yet),
 * - and you cannot commit the old version with changes, as the "skipped" 
 *   (later) changes will create conflicts in the repository.
 *
 *
 * \subsection rev_del Currently only known entries are handled.
 * 
 * If you need a switch (like \c --delete in \c rsync(1) ) to remove 
 * unknown (new, not yet versioned) entries, to get the directory in  the 
 * exact state it is in the repository, please tell the <tt>dev\@</tt> 
 * mailing list.  
 *
 * \todo Another limitation is that just-deleted just-committed entries 
 * cannot be fetched via \c revert, as FSVS no longer knows about them. \n
 * TODO: If a revision is given, take a look there, and ignore the local 
 * data? \n
 * As a workaround you could use the \ref cat "cat" and/or \ref checkout 
 * "checkout" commands to fetch repository-only data.
 *
 *
 * \subsection rev_p Removed directory structures
 *
 * If a path is specified whose parent is missing, \c fsvs complains. \n
 * We plan to provide a switch (probably \c -p), which would create (a 
 * sparse) tree up to this entry.
 *
 *
 * \subsection rev_rec Recursive behaviour
 * When the user specifies a non-directory entry (file, device, symlink), 
 * this entry is reverted to the old state.
 *
 * If the user specifies a directory entry, these definitions should apply:
 * <table>
 * <tr><th>command line switch<th>result
 * <tr><td>\c -N <td>  this directory only (meta-data),
 * <tr><td>none  <td> this directory, and direct children of the directory,
 * <tr><td>\c -R <td>  this directory, and the complete tree below.
 * </table>
 *
 *
 * \subsection rev_copied Working with copied entries
 * If an entry is marked as copied from another entry (and not committed!), 
 * a \c revert will fetch the original copyfrom source. To undo the copy 
 * setting use the \ref uncopy "uncopy" command.
 *
 * */


/** List of (bit-)flags for rev___undo_change().
 * These have an order, ie. SET_CURRENT overrides REVERT_MTIME. */
enum rev___dir_change_flag_e {
	NOT_CHANGED=0,
	REVERT_MTIME=1,
	SET_CURRENT=2,
	GET_TSTAMP=0x1000,
};

 
/** A count of files reverted in \b this run. */
static int number_reverted=0;
static svn_revnum_t last_rev;


#define REV___GETFILE_MAX_CACHE (4)


/** -.
 *
 * This function fetches an non-directory entry \a loc_url from the 
 * repository in \c current_url, and writes it to \a output - which gets 
 * closed via \c svn_stream_close(). 
 *
 * \a decoder should be set correctly.
 * \todo if it's \c NULL, but an update-pipe is set on the entry, the data 
 * has to be read from disk again, to be correctly processed.
 *
 * No meta-data is set, and the \c svn:special attribute is ignored.
 *
 * The revision number must be valid, it may not be \c SVN_INVALID_REVNUM.
 *
 * If \a sts_for_manber is \c NULL, no manber hashes are calculated.
 *
 * If \a output_sts is \c NULL, the meta-data properties are kept in \a 
 * props; else its fields are filled (as far as possible) with data. That 
 * includes the estat::repos_rev field.
 *
 * The user-specified properties can be returned in \a props.
 *
 * As this just returns the data in a stream, the files' type mostly 
 * doesn't matter; it just may not be a directory, because we'd get an 
 * error from subversion.
 *
 * \a loc_url must be given in the current locale; it will be converted to 
 * UTF8 before being sent to the subversion libraries. */
int rev__get_text_to_stream( char *loc_url, svn_revnum_t revision,
		const char *decoder,
		svn_stream_t *output,
		struct estat *sts_for_manber,
		struct estat *output_sts,
		apr_hash_t **props,
		apr_pool_t *pool)
{
	int status;
	svn_error_t *status_svn;
	svn_string_t *prop_val;
	struct encoder_t *encoder;
	char *utf8_url;
	apr_hash_t *properties;
	char target_rev[10];


	encoder=NULL;
	status=0;
	DEBUGP("getting file %s@%s from %s", loc_url, 
			hlp__rev_to_string(revision), current_url->url);


	if (strncmp(loc_url, "./", 2) == 0)
	{
		/* Skip ./ in front. */
	}
	else
	{
		/* It could be an absolute value. */

		/* Verify that the correct URL is taken.
		 * The "/" that's not stored at the end of the URL must be there, too.  
		 * */
		if (strncmp(current_url->url, loc_url, current_url->urllen) == 0 &&
				loc_url[current_url->urllen] == '/')
			loc_url += current_url->urllen+1;

		/* If the string doesn't match, it better be a relative value already 
		 * ... else we'll get an error.  */
		//	else STOPIF(EINVAL, "%s not below %s", loc_url, current_url->url);
	}

	STOPIF( hlp__local2utf8(loc_url, &utf8_url, -1), NULL);
	DEBUGP("Got utf8=%s", utf8_url);


	/* Symlinks have a MD5, too ... so just do that here. */
	/* How do we get the filesize here, to determine whether it's big
	 * enough for manber block hashing? */
	/* Short answer: We don't.
	 * We need to get the MD5 anyway; there's svn_stream_checksummed(),
	 * but that's just one chainlink more, and so we simply use our own
	 * function. */
	if (sts_for_manber)
		STOPIF( cs__new_manber_filter(sts_for_manber, 
					output, &output, pool), NULL);	


	/* If there's a fsvs:update-pipe, we would know when we have the file 
	 * here - which is a bit late, because we'd have to read/write the entire 
	 * file afresh. So we remember the property in the cb__record_changes() 
	 * call chain, and look for the string here. 
	 *
	 * But that works only if we *know* that we're processing the right 
	 * version. If the filter changed for this file, we might try to decode 
	 * with the wrong one - eg. for diff, where multiple versions are handled 
	 * in a single call.
	 * 
	 * We know that we have the correct value locally if the wanted revision 
	 * is the same as we've in the entry; if they are different, we have to 
	 * ask the repository for the data.
	 *
	 *
	 * Note: we're trading network-round-trips for local disk bandwidth.
	 * The other way would be to fetch the data encoded, *then* look in the 
	 * properties we just got for the pipe-command, and re-pipe the file 
	 * through the command given.
	 *
	 * But: the common case of updates uses cb__record_changes(), which 
	 * already gets the correct value. So in this case we need not look any 
	 * further.
	 */
	/* \todo For things like export we could provide a commandline parameter; 
	 * use network, or use disk.
	 * For a local-remote diff we could pipe the data into the diff program; 
	 * but that wouldn't work for remote-remote diffing, as diff(1) doesn't 
	 * accept arbitrary filehandles as input (and /proc/self/fd/ isn't 
	 * portable). */

	/* Fetch decoder from repository. */
	if (decoder == DECODER_UNKNOWN)
	{
		STOPIF_SVNERR_TEXT( svn_ra_get_file,
				(current_url->session,
				 utf8_url, revision,
				 NULL,
				 &revision, &properties,
				 pool),
			 "Fetching entry \"%s/%s\"@%s",	
			 current_url->url,
			 loc_url, hlp__rev_to_string(revision));

		prop_val=apr_hash_get(properties, propval_updatepipe, APR_HASH_KEY_STRING);
		decoder=prop_val ? prop_val->data : NULL;
	}


	/* First decode, then do manber-hashing. As the filters are prepended, we 
	 * have to do that after the manber-filter. */
	if (decoder)
	{
		snprintf(target_rev, sizeof(target_rev), 
				"%llu", (t_ull)revision);
		setenv(FSVS_EXP_TARGET_REVISION, target_rev, 1);

		STOPIF( hlp__encode_filter(output, decoder, 1, 
					loc_url, &output, &encoder, pool), NULL);
		if (output_sts)
			encoder->output_md5= &(output_sts->md5);
	}


	STOPIF_SVNERR_TEXT( svn_ra_get_file,
			(current_url->session,
			 utf8_url, revision,
			 output,
			 &revision, &properties,
			 pool),
			"Fetching entry %s/%s@%s",	
			current_url->url,
			loc_url, hlp__rev_to_string(revision));
	DEBUGP("got revision %llu", (t_ull)revision);

	/* svn_ra_get_file doesn't close the stream. */
	STOPIF_SVNERR( svn_stream_close, (output));
	output=NULL;

	if (output_sts)
	{
		output_sts->repos_rev = revision;
		STOPIF( prp__set_from_aprhash( output_sts, properties, 
					ONLY_KEEP_USERDEF, NULL, pool), NULL);
	}

	if (props)
		*props=properties;


ex:
	return status;
}


/** -.
 * Mostly the same as \c rev__get_text_to_stream(), but returning a 
 * (temporary) \a filename based on \a filename_base, if this is not \c 
 * NULL.
 *
 * The entries' file type isn't taken into account; the file may have the 
 * data <tt>"symlink XXX"</tt>, etc.
 *
 * If \a filename_base is \c NULL, the file will be put in a real temporary 
 * location.
 *
 * \a output_stat is used to store the parsed properties of the entry.
 * */
int rev__get_text_to_tmpfile(char *loc_url, svn_revnum_t revision,
		char *encoder,
		char *filename_base, char **filename,
		struct estat *sts_for_manber, 
		struct estat *output_sts, apr_hash_t **props,
		apr_pool_t *pool)
{
	int status;
	apr_file_t *apr_f;
	svn_stream_t *output;


	status=0;

	STOPIF( waa__get_tmp_name( filename_base, filename, &apr_f, pool), NULL);
	output=svn_stream_from_aprfile(apr_f, pool);

	STOPIF( rev__get_text_to_stream( loc_url, revision, encoder,
				output, sts_for_manber, output_sts, props, pool), NULL);

	/* svn_ra_get_file() doesn't close. */
	STOPIF( apr_file_close(apr_f), NULL);

ex:
	return status;
}


/** -.
 *
 * Does no validation of input - might fill entire memory. */
int rev__get_text_into_buffer(char *loc_url, svn_revnum_t revision,
		const char *decoder,
		svn_stringbuf_t **output,
		struct estat *sts_for_manber,
		struct estat *output_sts,
		apr_hash_t **props,
		apr_pool_t *pool)
{
	int status;
	svn_stringbuf_t *string;
	svn_stream_t *stream;

	status=0;
	string=svn_stringbuf_create("", pool);
	stream=svn_stream_from_stringbuf(string, pool);

	STOPIF( rev__get_text_to_stream(loc_url, revision,
				decoder, stream, sts_for_manber, output_sts, props, pool), NULL);

	*output=string;
ex:
	return status;
}


/** -.
 *
 * Meta-data is set; an existing local entry gets atomically removed by \c 
 * rename().
 *
 * If the entry has no URL defined yet, but has a copy flag set (\c 
 * RF_COPY_BASE or \c RF_COPY_SUB), this URL is taken.
 *
 * If \a revision is 0, the \c BASE revision is and \a decoder is used; 
 * this is the copy base for copied entries.
 */
int rev__install_file(struct estat *sts, svn_revnum_t revision,
		char *decoder,
		apr_pool_t *pool)
{
	int status;
	char *filename;
	char *filename_tmp;
	apr_hash_t *props;
	svn_stream_t *stream;
	apr_file_t *a_stream;
	apr_pool_t *subpool;
	char *special_data;
	char *url;
	svn_revnum_t rev_to_take;


	BUG_ON(!pool);
	STOPIF( ops__build_path(&filename, sts), NULL);


	/* We know that we have to do something here; but because the order is 
	 * depth-first, the parent directory isn't done yet (and shouldn't be, 
	 * because it needs permissions and mtime set!).
	 * So it's possible that the target directory doesn't yet exist.
	 *
	 * Note: because we're here for *non-dir* entries, we always have a 
	 * parent. */
	STOPIF( waa__mkdir(filename, 0), NULL);


	STOPIF( apr_pool_create(&subpool, pool),
			"Creating the filehandle pool");


	/* When we get a file, old manber-hashes are stale.
	 * So remove them; if the file is big enough, we'll recreate it with 
	 * correct data. */
	STOPIF( waa__delete_byext(filename, WAA__FILE_MD5s_EXT, 1), NULL);


	/* Files get written in files; we use the temporarily generated name for  
	 * special entries, too. */
	/* We could use a completely different mechanism for temp-file-names;
	 * but keeping it close to the target lets us see if we're out of
	 * disk space in this filesystem. (At least if it's not a binding mount
	 * or something similar - but then rename() should fail).
	 * If we wrote the data somewhere else, we'd risk moving it again, across 
	 * filesystem boundaries. */
	STOPIF( waa__get_tmp_name( filename, &filename_tmp, &a_stream, subpool), 
			NULL);


	/* It's a bit easier to just take the (small) performance hit, and always 
	 * (temporarily) write the data in a file.
	 * If it's a special entry, that will just get read immediately back and 
	 * changed to the correct type.
	 *
	 * It doesn't really make much difference, as the file is always created 
	 * to get a distinct name. */
	stream=svn_stream_from_aprfile(a_stream, subpool);


	if (sts->url)
	{
		url=filename+2;
		rev_to_take=sts->repos_rev;
		current_url=sts->url;
	}
	else if (sts->flags & RF___IS_COPY)
	{
		STOPIF( cm__get_source( sts, filename, &url, &rev_to_take, 0), NULL);
		STOPIF( url__find( url, &current_url), NULL);
	}
	else
		BUG("cannot get file %s", filename);

	if (revision == 0) 
	{
		/* BASE wanted; get decoder. */
		STOPIF( up__fetch_decoder(sts), NULL);
		decoder=sts->decoder;
	}
	else
	{
		/* Arbitrary revision - get decoder. */
		rev_to_take=revision;
		decoder=DECODER_UNKNOWN;
	}


	STOPIF( url__open_session(NULL, NULL), NULL);

	/* We don't give an estat for meta-data parsing, because we have to loop 
	 * through the property list anyway - for storing locally. */
	STOPIF( rev__get_text_to_stream( url, rev_to_take, decoder, 
				stream, sts, NULL, &props, pool), NULL);


	if (apr_hash_get(props, propname_special, APR_HASH_KEY_STRING))
	{
		STOPIF( ops__read_special_entry( a_stream, &special_data, 
					0, NULL, filename_tmp, subpool), NULL);

		/* The correct type gets set on parsing. */
		STOPIF( up__handle_special(sts, filename_tmp, 
					special_data, subpool), NULL);
	}
	else
	{
		/* If it's not special, it must be an ordinary file. */
		/* This is a kind of default value, the mode is set to the repository 
		 * value in up__set_meta_data(). */
		sts->st.mode = (sts->st.mode & ~S_IFMT) | S_IFREG;
		sts->local_mode_packed=sts->new_rev_mode_packed=
			MODE_T_to_PACKED(sts->st.mode);
	}


	STOPIF( prp__set_from_aprhash(sts, props, STORE_IN_FS, 
				NULL, subpool), NULL);


	/* We write all meta-data. If we got no values from the repository, we just
	 * write what we have in the local filesystem back - the temporary file has
	 * just some default values, after all. */
	sts->remote_status |= FS_META_CHANGED;
	DEBUGP("setting meta-data");
	STOPIF( up__set_meta_data(sts, filename_tmp), NULL);

	STOPIF( apr_file_close(a_stream), NULL);


	DEBUGP("rename to %s", filename);
	/* rename to correct filename */
	STOPIF_CODE_ERR( rename(filename_tmp, filename)==-1, errno,
			"Cannot rename '%s' to '%s'", filename_tmp, filename);

	/* The rename changes the ctime. */
	STOPIF( hlp__lstat( filename, &(sts->st)),
			"Cannot lstat('%s')", filename);


	sts->url=current_url;
	/* We have to re-sort the parent directory, as the inode has changed
	 * after an rename(). */
	sts->parent->to_be_sorted=1;

	apr_pool_destroy(subpool);
	subpool=NULL;


ex:
	/* On error remove the temporary file. */
	/* Return the original error. */
	if (status)
		unlink(filename_tmp);

	return status;
}


/** -.
 *
 * The base name of the \a sts gets written to.
 *
 * If the merge gives no errors, the temporary files get deleted.
 * */
int rev__merge(struct estat *sts,
		const char *file1, 
		const char *common, 
		const char *file2)
{
	int status;
	pid_t pid;
	char *output;
	int hdl;
	struct sstat_t stat;
	int retval;


	STOPIF( ops__build_path(&output, sts), NULL);

	/* Remember the meta-data of the target */
	STOPIF( hlp__lstat(file2, &stat), NULL);


	pid=fork();
	STOPIF_CODE_ERR( pid == -1, errno, "Cannot fork()" );
	if (pid == 0)
	{
		/* Child. */
		/* TODO: Is there some custom merge program defined?
		 * We always use the currently defined property. */
		/* TODO: how does that work if an update sends a wrong property? use 
		 * both? */

		/* Open the output file. */
		hdl=open(output, O_WRONLY | O_CREAT, 0700);
		STOPIF_CODE_ERR( hdl == -1, errno, 
				"Cannot open merge output \"%s\"", output);
		STOPIF_CODE_ERR( dup2(hdl, STDOUT_FILENO) == -1, errno,
				"Cannot dup2");
		/* No need to close hdl -- it's opened only for that process, and will 
		 * be closed when it exec()s. */

		/* Remove the ./ at the front */
		setenv(FSVS_EXP_CURR_ENTRY, output+2, 1);

		STOPIF_CODE_ERR( execlp( opt__get_string(OPT__MERGE_PRG), 
					opt__get_string(OPT__MERGE_PRG),
					opt__get_string(OPT__MERGE_OPT),
					file1, common, file2,
					NULL) == -1, errno,
				"Starting the merge program \"%s\" failed",
				opt__get_string(OPT__MERGE_PRG));

	}

	STOPIF_CODE_ERR( pid != waitpid(pid, &retval, 0), errno, "waitpid");

	DEBUGP("merge returns %d (signal %d)", 
			WEXITSTATUS(retval), WTERMSIG(retval));

	/* Can that be? */
	STOPIF_CODE_ERR( WIFSIGNALED(retval) || !WIFEXITED(retval), EINVAL, 
			"\"%s\" quits by signal %d.", 
			opt__get_string(OPT__MERGE_PRG),
			WTERMSIG(retval));

	if (WEXITSTATUS(retval) == 0)
	{
		DEBUGP("Remove temporary files.");

		/* Ok, merge done. Remove temporary files, or at least try to. */
		if (unlink(file1) == -1) status=errno;
		if (unlink(file2) == -1) status=errno;
		if (unlink(common) == -1) status=errno;
		STOPIF(status, "Removing one or more temporary files "
				"(merge of \"%s\") failed", output);
	}
	else
	{
		DEBUGP("non-zero return");
		STOPIF_CODE_ERR( WEXITSTATUS(retval) != 1, EINVAL,
				"\"%s\" exited with error code %d",
				opt__get_string(OPT__MERGE_PRG),
				WEXITSTATUS(retval));

		STOPIF( res__mark_conflict(sts, 
					file1, file2, common, NULL), NULL);

		/* Means merge conflicts, but no error. */
	}

	/* As we've just changed the text, set the current mtime. */
	sts->st.mtim.tv_sec=time(NULL);
	/* Now set owner, group, and mode.
	 * This does a lstat(), to get the current ctime and so on;
	 * to make the changes visible, we use the meta-data of the target. */
	STOPIF( up__set_meta_data(sts, NULL), NULL);
	sts->st=stat;


ex:
	return status;
}


/** -. 
 * */
int rev__get_props(struct estat *sts, 
		char *utf8_path,
		svn_revnum_t revision,
		apr_pool_t *pool)
{
	int status;
	svn_error_t *status_svn;
	apr_hash_t *props;
	char *filename;


	if (!utf8_path)
	{
		STOPIF( ops__build_path(&filename, sts), NULL);
		STOPIF( hlp__local2utf8(filename+2, &utf8_path, -1), NULL);
	}

	STOPIF_SVNERR( svn_ra_get_file,
			(current_url->session,
			 utf8_path,
			 revision,
			 NULL, 
			 NULL,
			 &props,
			 pool) );
	STOPIF( prp__set_from_aprhash(sts, props, STORE_IN_FS, NULL, pool), NULL);

ex:
	return status;
}


/** Set, reset or fetch the mtime of a directory.
 * */
int rev___handle_dir_mtime(struct estat *dir,
		enum rev___dir_change_flag_e dir_flag)
{
	int status;
	char *path;


	/* Now, after all has been said and done for the children, set and re-get 
	 * the actual meta-data - the mtime has been changed in the meantime 
	 * (because of child node creation), and maybe this filesystem's 
	 * granularity is worse than on commit; then the timestamps would be 
	 * wrong. */
	status=0;
	DEBUGP("dir_flag says %X", dir_flag);


	if (dir_flag & SET_CURRENT) goto a;
	if (dir_flag & REVERT_MTIME) goto b;
	if (dir->remote_status & FS_META_CHANGED) goto c;
	if (dir_flag & GET_TSTAMP) goto d;
	/* Is there some better syntax? Some kind of switch with 
	 * case-expressions?
	 *
	 * I had a lot of if () { } with partially-overlapping conditions:
	 *   if (dir->flag &  x) A();
	 *   if (dir->flag & (x|y)) B();
	 * but gcc wouldn't simply emit a "jmp" to B() after the A() - and I 
	 * couldn't easily see that the statements were accumulative.
	 * */
	goto x;

a: 
	/* If there's an intentional change (like merging), the current time is 
	 * taken. */
	time( & dir->st.mtim.tv_sec );
b:
	/* Make sure that the value is written back to the filesystem.*/
	dir->remote_status |= FS_META_MTIME;
c:
	STOPIF( up__set_meta_data(dir, NULL), NULL);
d:
	/* ops__update_single_entry() would trash the entry_status field! */
  STOPIF( ops__build_path(&path, dir), NULL);
	STOPIF( hlp__lstat(path, &dir->st), NULL);

	/* If it had changes, we'll have to check next time. */
	if (dir->entry_status & FS_CHANGED)
		dir->flags |= RF_CHECK;

x:

ex:
	return status;
}


/** Revert action, called for every wanted entry.
 * Please note that contacting the repository is allowed, as we're only 
 * looping through the local entries. 
 * 
 * Doing operations against the repository while being called *from* the ra 
 * layer (eg. during an update) is not allowed! See also \c 
 * svn_ra_do_update():
 * \code
 * The caller may not perform any RA operations using @a session before
 * finishing the report, and may not perform any RA operations using
 * @a session from within the editing operations of @a update_editor.
 * \endcode
 *
 * We may not change \c sts->entry_status - the caller still needs it; and 
 * as this is a revert to \c BASE, we must not modify the entry list 
 * either.
 * */
int rev___revert_to_base(struct estat *sts,
		enum rev___dir_change_flag_e *dir_change_flag,
		apr_pool_t *pool)
{
	int status;
	svn_revnum_t wanted;
	char *path;


	status=0;
	STOPIF( ops__build_path(&path, sts), NULL);

	/* Garbage collection for entries that should be ignored happens in 
	 * waa__output_tree(); changing the tree while it's being traversed is 
	 * a bit nasty. */

	if ( (sts->flags & RF_UNVERSION))
	{
		/* Was marked as to-be-unversioned? Just keep it. */
		sts->flags &= ~RF_UNVERSION;
		DEBUGP("removing unversion on %s", path);
	}
	else if ( sts->flags & RF_ADD )
	{
		/* Added entry just gets un-added ... ie. unknown. */
		sts->to_be_ignored=1;
		DEBUGP("removing add-flag on %s", path);
	}
	else if (!( (sts->flags & (RF_COPY_BASE | RF_COPY_SUB)) || sts->url ) )
	{
		/* We have no URL, and no copyfrom source ... this is an unknown entry.
		 * Has to be given directly on the command line, but could have happened 
		 * via a wildcard - so don't stop working.
		 * Can't do anything about it. */
		printf("Cannot revert unknown entry \"%s\".\n", path);
		status=0;
		goto ex;
	}
	else
	{
		/* We know where to get that from. */
		DEBUGP("have an URL for %s", path);

		if ( sts->flags & RF_CONFLICT )
		{
			*dir_change_flag |= REVERT_MTIME;
			STOPIF( res__remove_aux_files(sts), NULL);
		}

		/* If not seen as changed, but target is BASE, we don't need to do 
		 * anything. */
		if (!opt_target_revisions_given &&
				!(sts->entry_status & FS__CHANGE_MASK))
			goto ex;


		wanted=opt_target_revisions_given ? opt_target_revision : sts->repos_rev;
		/* The base directory has no revision, and so can't have a meaningful 
		 * value printed. */
		/* In case we're doing a revert which concernes multiple URLs, they might 
		 * have different BASE revisions.
		 * Print the current revision. */


		if (sts->parent && (!number_reverted || last_rev != wanted))
		{
			if (opt__verbosity() > VERBOSITY_VERYQUIET)
				printf("Reverting to revision %s:\n", hlp__rev_to_string(wanted));
			last_rev=wanted;
		}
		number_reverted++;


		DEBUGP("l_st=%s, r_st=%s, old=%p", 
				st__status_string_fromint(sts->entry_status), 
				st__status_string_fromint(sts->remote_status), 
				sts->old);

		/* Parent directories might just have been created. */
		if (!S_ISDIR(sts->st.mode))
		{
			DEBUGP("file was changed, reverting");

			/* \todo It would be nice if we could solve meta-data *for the current 
			 * revision* only changes without going to the repository - after all, 
			 * we know the old values.
			 * \todo Maybe we'd need some kind of parameter, --meta-only? Keep 
			 * data, reset rights.
			 * */
			/* TODO - opt_target_revision ? */
			STOPIF( rev__install_file(sts, wanted, sts->decoder, pool),
					"Unable to revert entry '%s'", path);
			*dir_change_flag |= REVERT_MTIME;
		}
		else
		{
#if 0
			if (sts->entry_status & FS_NEW)
				conflict();
#endif
			if (sts->entry_status & FS_REMOVED)
			{
//				sts->st.mode ist 040755 (file); old ist NULL.
				status = (mkdir(path, sts->st.mode & 07777) == -1) ? errno : 0;
				if (status == EEXIST)
				{
				DEBUGP("old=%p", sts->old);
				}
				DEBUGP("mkdir(%s) says %d", path, status);
				STOPIF(status, "Cannot create directory '%s'", path);
				*dir_change_flag |= REVERT_MTIME;

				/* As we just created the directory, we need *all* meta-data reset.  
				 * */
				sts->remote_status |= FS_META_CHANGED;
			}
			else
			{
				/* Code for directories.
				 * As the children are handled by the recursive options and by \a 
				 * ops__set_to_handle_bits(), we only have to restore the directories' 
				 * meta-data here. */
				/* up__set_meta_data() checks remote_status, while we here have 
				 * entry_status set. */
				sts->remote_status=sts->entry_status;
			}

			STOPIF( up__set_meta_data(sts, NULL), NULL);
			if (sts->entry_status)
				sts->flags |= RF_CHECK;
		}
	}

	/* There's no change anymore, we're at BASE.
	 * But just printing "...." makes no sense ... show the old status. */
	sts->flags |= RF_PRINT;

ex:
	return status;
}


/** Reset local changes. */
int rev___no_local_change(struct estat *sts)
{
  sts->entry_status=0;
	return st__progress(sts);
}


/** -.
 * Recurses for rev___revert_to_base.
 *
 * There's a bit of uglyness here, regarding deleted directories ...
 *
 * 1) If we do the tree depth-first, we have to build multiple levels of 
 * directories at once - and store which have to have their meta-data 
 * reset.
 *
 * 2) If we do level after level, we might end up with either
 * a) re-creating a directory, doing its children, then have to re-set the 
 * meta-data of this directory, or
 * b) just store that the meta-data has to be done for later.
 *
 * Currently we do 2a - that seems the simplest, and has no big performance 
 * penalty. */
int rev___local_revert(struct estat *dir, 
		apr_pool_t *pool)
{
	int status;
	int i, do_undo;
	struct estat *sts;
	apr_pool_t *subpool;
	enum rev___dir_change_flag_e dir_flag;


	status=0;
	subpool=NULL;
	dir_flag= NOT_CHANGED;

	for(i=0; i<dir->entry_count; i++)
	{
		sts=dir->by_inode[i];
		STOPIF( apr_pool_create(&subpool, pool), "Cannot get a subpool");

		do_undo = sts->do_this_entry && 
			(sts->entry_status & FS__CHANGE_MASK) &&
			ops__allowed_by_filter(sts);

		DEBUGP("on %s: do_undo=%d, st=%s", sts->name, do_undo,
				st__status_string_fromint(sts->entry_status));

		if (do_undo)
			STOPIF( rev___revert_to_base(sts, &dir_flag, subpool), NULL);

		if (S_ISDIR(sts->st.mode) && 
				(sts->entry_status & FS_CHILD_CHANGED))
			STOPIF( rev___local_revert(sts, subpool), NULL);
	
		if (do_undo)
			STOPIF( st__status(sts), NULL);


		apr_pool_destroy(subpool);
		subpool=NULL;
	}

	/* We cannot free the memory earlier - the data is needed for the status 
	 * output and recursion. */
	STOPIF( ops__free_marked(dir, 0), NULL);

	/* The root entry would not be printed; do that here. */
	if (!dir->parent)
		STOPIF( st__status(dir), NULL);


	STOPIF( rev___handle_dir_mtime(dir, dir_flag), NULL);

ex:
	return status;
}


/** -.
 * Loads the stored tree (without updating), looks for the wanted entries,
 * and restores them from the repository. */
int rev__work(struct estat *root, int argc, char *argv[])
{
	int status;
	char **normalized;
	time_t delay_start;
	svn_revnum_t rev;


	status=0;
	/* For revert the default is non-recursive. */
	opt_recursive--;

	if (!argc) ac__Usage_this();

	STOPIF( waa__find_common_base(argc, argv, &normalized), NULL);

	STOPIF( url__load_nonempty_list(NULL, 0), NULL);

	if (opt_target_revisions_given)
	{
		STOPIF( wa__warn( WRN__MIXED_REV_WC, EINVAL,
					"Sorry, fsvs currently doesn't allow mixed revision working copies.\n"
					"Entries will still be compared against the BASE revision.\n"),
				NULL);

		// TODO: necessary?
		action->local_callback=rev___no_local_change;
	}
	else
	{
		/* No revision given - just go back to BASE. */
		action->local_callback=st__progress;
	}


	/* This message can be seen because waa__find_common_base() looks for
	 * an "url" file and not for a "dir" -- which means that this tree
	 * was never committed, so we don't know what HEAD is. */
	/* Maybe the user could still try with some revision number and we simply
	 * check for the existence of the given path there? */
	status=waa__read_or_build_tree(root, argc, normalized, argv, NULL, 1);
	if (status == -ENOENT)
		STOPIF(status,
				"!We know nothing about previous or current versions, as this tree\n"
				"was never checked in.\n"
				"If you need such an entry reverted, you could either write the needed\n"
				"patch (and send it to dev@fsvs.tigris.org), or try with a 'sync-repos'\n"
				"command before (if you know a good revision number)\n");
	else
		STOPIF(status, NULL);

	STOPIF( st__progress_uninit(), NULL);


	if (opt_target_revisions_given)
	{
		while ( ! ( status=url__iterator(&rev) ) )
		{
			STOPIF( cb__record_changes(root, rev, current_url->pool), NULL);
		}
		STOPIF_CODE_ERR( status != EOF, status, NULL);

		STOPIF( rev__do_changed(root, global_pool), NULL);
	}
	else
	{
		/* The local changes are taken as to be undone.
		 *
		 * We cannot go by estat::entry_status - things like RF_ADD have to be 
		 * undone, too.
		 *
		 * waa__do_sorted_tree() can't be used, either, because it does the 
		 * directory *before* the children - which makes the directories' mtime 
		 * wrong if children get created or deleted. */
		STOPIF( rev___local_revert(root, global_pool), NULL);
	}

	
	/* If this was a revert with destination revision, we might have changed 
	 * the entire hierarchy - replaced directories with files, etc.
	 * This changed tree must not be written, because it's not the state of 
	 * BASE.
	 *   [ And if we had to write the original (BASE) list for some cause,
	 *     we'd have to read the list afresh, and change what we have to.
	 *     Or, the other way: when getting the changes for the given revision 
	 *     from the repository we'd have to put them in the estat::old shadow 
	 *     tree, to keep the entry list correct. ]
	 *
	 * If this was a revert to BASE, we have to write the list, because the 
	 * ctime of the inodes will be changed - and would mark the entries as 
	 * "maybe changed". */
	if (!opt_target_revisions_given)
	{
		delay_start=time(NULL);
		STOPIF( waa__output_tree(root), NULL);
		STOPIF( hlp__delay(delay_start, DELAY_REVERT), NULL);
	}

ex:
	return status;
}


/** Takes the \c sts->remote_status, and does the changes mentioned there.
 * Depending on \c sts->entry_status a conflict might be set.
 *
 * Convenience function to reduce indenting.  */
int rev___undo_change(struct estat *sts, 
		enum rev___dir_change_flag_e *dir_change_flag,
		apr_pool_t *pool)
{
	int status;
	char *fn;
	const char *unique_name_mine, 
				*unique_name_remote, 
				*unique_name_common;
	char revnum[12];
	int j;
	struct estat *removed;
	struct sstat_t st;


	STOPIF( ops__build_path( &fn, sts), NULL);
	DEBUGP_dump_estat(sts);

	/* If we remove an entry, the entry_count gets decremented; 
	 * we have to repeat the loop *for the same index*. */


	unique_name_mine=NULL;

	/* Conflict handling; depends whether it has changed locally. */
	if (sts->entry_status & FS_CHANGED)
		switch (opt__get_int(OPT__CONFLICT))
		{
			case CONFLICT_STOP:
				STOPIF( EBUSY, "!The entry %s has changed locally", fn);
				break;

			case CONFLICT_LOCAL:
				/* Next one, please. */
				STOPIF_CODE_EPIPE( printf("Conflict for %s skipped.\n", fn), NULL);
				goto ex;

			case CONFLICT_REMOTE:
				/* Just ignore local changes. */
				break;

			case CONFLICT_MERGE:
			case CONFLICT_BOTH:
				/* Rename local file to something like .mine. */
				STOPIF( hlp__rename_to_unique(fn, ".mine", 
							&unique_name_mine, pool), NULL);
				/* Now the local name is not used ... so get the file. */
				break;

			default:
				BUG("unknown conflict resolution");
		}


	/* If the entry has been removed in the repository, we remove it
	 * locally, too (if it wasn't changed).
	 * But the type in the repository may be another than the local one -
	 * so we have to check what we currently have. */
	/* An entry can be given as removed, and in the same step be created
	 * again - possibly as another type. */

	/* If the entry wasn't replaced, but only removed, there's no sts->old. 
	 * */
	removed=sts->old ? sts->old : sts;
	if (removed->remote_status & FS_REMOVED)
	{
		/* Is the entry already removed? */
		/* If there's a typechange involved, the old entry has been 
		 * renamed, and so doesn't exist in the filesystem anymore. */
		if ((sts->entry_status & FS_REPLACED) != FS_REMOVED &&
				!unique_name_mine)
		{
			/* Find type. Small race condition - it might be removed now. */
			if (TEST_PACKED(S_ISDIR, removed->old_rev_mode_packed))
			{
				STOPIF( up__rmdir(removed, sts->url), NULL);
			}
			else
				STOPIF( up__unlink(removed, fn), NULL);
		}

		*dir_change_flag|=REVERT_MTIME;
	}


	/* Is there some kind of garbage that has to be removed? */
	if (TEST_PACKED(S_ISGARBAGE, sts->local_mode_packed))
	{
		DEBUGP("cleaning garbage");
		STOPIF_CODE_ERR( unlink(fn) == -1, errno,
				"Cannot remove garbage entry %s", fn);
	}



	/* If we change something in this directory, we have to re-sort the 
	 * entries by inode again. */
	sts->parent->to_be_sorted=1;

	if ((sts->remote_status & FS_REPLACED) == FS_REMOVED)
	{
		sts->to_be_ignored=1;
		goto ex;
	}
	current_url=sts->url;

	if (S_ISDIR(sts->st.mode))
	{
		*dir_change_flag|=REVERT_MTIME;
		STOPIF( waa__mkdir_mask(fn, 1, sts->st.mode), NULL);

		/* Meta-data is done later. */

		/* An empty directory need not be sorted; if we get entries,
		 * we'll mark it with \c to_be_sorted .*/
	}
	else if (sts->remote_status & (FS_CHANGED | FS_REPLACED))
		/* Not a directory */
	{
		STOPIF( rev__install_file(sts, 0, sts->decoder, pool), NULL);
		*dir_change_flag|=REVERT_MTIME;

		/* We had a conflict; rename the file fetched from the 
		 * repository to a unique name. */
		if (unique_name_mine)
		{
			*dir_change_flag|=SET_CURRENT;

			/* If that revision number overflows, we've got bigger problems.  
			 * */
			snprintf(revnum, sizeof(revnum)-1, 
					".r%llu", (t_ull)sts->repos_rev);
			revnum[sizeof(revnum)-1]=0;

			STOPIF( hlp__rename_to_unique(fn, revnum,
						&unique_name_remote, pool), NULL);

			/* If we're updating and already have a conflict, we don't 
			 * merge again. */
			if (sts->flags & RF_CONFLICT)
			{
				STOPIF_CODE_EPIPE(
						printf("\"%s\" already marked as conflict.\n", fn), 
						NULL);
				STOPIF( res__mark_conflict(sts, 
							unique_name_mine, unique_name_remote, NULL), NULL);
			}
			else if (opt__get_int(OPT__CONFLICT) == CONFLICT_BOTH)
			{
				STOPIF( res__mark_conflict(sts, 
							unique_name_mine, unique_name_remote, NULL), NULL);

				/* Create an empty file,
				 * a) to remind the user, and
				 * b) to avoid a "Deleted" status. */
				j=creat(fn, 0777);
				if (j != -1) j=close(j);

				STOPIF_CODE_ERR(j == -1, errno, 
						"Error creating \"%s\"", fn);

				/* up__set_meta_data() does an lstat(), but we want the 
				 * original values. */
				st=sts->st;
				STOPIF( up__set_meta_data(sts, fn), NULL);
				sts->st=st;
			}
			else if (opt__get_int(OPT__CONFLICT) == CONFLICT_MERGE)
			{
				STOPIF( rev__install_file(sts, sts->old_rev, 
							NULL, pool), NULL);

				snprintf(revnum, sizeof(revnum)-1, 
						".r%llu", (t_ull)sts->old_rev);
				revnum[sizeof(revnum)-1]=0;

				STOPIF( hlp__rename_to_unique(fn, revnum,
							&unique_name_common, pool), NULL);

				STOPIF( rev__merge(sts, 
							unique_name_mine, 
							unique_name_common, 
							unique_name_remote), NULL);
			}
			else
				BUG("why a conflict?");
		}
	}
	else 
	{
		/* If user-defined properties have changed, we have to fetch them 
		 * from the repository, as we don't store them in RAM (due to the  
		 * amount of memory possibly needed). */
		if (sts->remote_status & FS_PROPERTIES)
			STOPIF( rev__get_props(sts, NULL, sts->repos_rev, pool), NULL);

		if (sts->remote_status & FS_META_CHANGED)
		{
			/* If we removed the file, it has no meta-data any more;
			 * if we fetched it via rev__get_file(), it has it set already.
			 * Only the case of *only* meta-data-change is to be done. */
			STOPIF( up__set_meta_data(sts, fn), NULL);
		}
	}


ex:
	return status;
}


/** -.
 * Used on update. */
int rev__do_changed(struct estat *dir, 
		apr_pool_t *pool)
{
	int status;
	int i;
	struct estat *sts;
	apr_pool_t *subpool;
	enum rev___dir_change_flag_e dir_flag;


	status=0;
	subpool=NULL;
	dir_flag= (dir->entry_status & FS_NEW) || 
		(dir->remote_status & FS_NEW) ? REVERT_MTIME : NOT_CHANGED;

	/* If some children have changed, do a full run.
	 * Else just repair meta-data. */
	if (!(dir->remote_status & FS_CHILD_CHANGED))
		DEBUGP("%s: no children changed", dir->name);
	else for(i=0; i<dir->entry_count; i++)
	{
		sts=dir->by_inode[i];

		STOPIF( apr_pool_create(&subpool, pool), "Cannot get a subpool");

		if (sts->remote_status & FS__CHANGE_MASK)
			STOPIF( rev___undo_change(sts, &dir_flag, subpool), NULL);

		/* We always recurse now, even if the directory has no children.
		 * Else we'd have to check for children in a few places above, which would
		 * make the code unreadable. */
		if (S_ISDIR(sts->st.mode) &&
				(sts->remote_status & FS_REPLACED) != FS_REMOVED)
		{
			apr_pool_destroy(subpool);
			subpool=NULL;
			STOPIF( apr_pool_create(&subpool, pool), "subpool creation");

			STOPIF( rev__do_changed(sts, subpool), NULL);
		}	

		STOPIF( st__rm_status(sts), NULL);

		apr_pool_destroy(subpool);
		subpool=NULL;
	}

	/* We cannot free the memory earlier - the data is needed for the status 
	 * output and recursion. */
	STOPIF( ops__free_marked(dir, 0), NULL);

	/* The root entry would not be printed; do that here. */
	if (!dir->parent)
		STOPIF( st__rm_status(dir), NULL);

	/* If the directory had local modifications, we need to check it 
	 * next time -- as we take its current timestamp,
	 * we'd miss the new or deleted entries. 
	 * Must be done before \c ops__update_single_entry() - That sets 
	 * \c dir->entry_status .*/
	if (dir->entry_status & FS__CHANGE_MASK)
		dir->flags |= RF_CHECK;

	STOPIF( rev___handle_dir_mtime(dir, dir_flag), NULL);


ex:
	return status;
}