NAME
    patcher - a patch maintenance tool

SYNOPSIS
    patcher [-n <patchname>] [<file ...>]
                        Edit <file> as part of the patch <patchname>.

    patcher -r          Refresh current patch.

    patcher [-f] -b     Move back one patch to the previous one.

    patcher [-f] -b <patch>
                        Move back in series until we're at <patch>.

    patcher [-f] -b <num>
                        Move back <num> patches in series.

    patcher -a          Apply the next patch in the series.

    patcher -a <patch>  Apply all patches from the series until we've
                        reached at <patch>.

    patcher -a <num>    Apply next <num> patches from series.

    patcher -n <patchname> [-p <n>] -i <diff>
                        Import an external diff file into patch <patchname>.
                        Strip <n> levels from the directory names. Please
                        note that patch allows '-p1', but we only '-p 1'.

    patcher [-f] [-n <patchname>] [-p <n>] -i <patch ...>
                        Import an external diff file into patch <patchname>.
                        Strip <n> levels from the directory names. Please
                        note that patch allows '-p1', but we only '-p 1'.

CONCEPT
    Patcher is a perl script which I use for managing patches. It's quite
    powerful, easy to use, and fast.

    Patcher keeps track of which files you change. It then can generate
    patches from your changes, no need for you to handle the diff tool
    manually.

    You can have more than one record of file changes, we call this a patch.
    A patch is something that the patch(1) command can apply.

    The patches can be stacked in series, they define the order they have to
    applied. Patcher keeps series information as well as information which
    patches have been applied and which not.

DESCRIPTION
    Later we will have a walkthrought, but let me first explain the basic
    operation modes of patcher:

  Editing files

    When you call patcher with a filename, patch will make a backup of this
    file (if the file exists). Now you can create or change the file. Later
    you can ask patcher to create a unified diff with all your changes.

  Creating unified diffs

    Just call "patcher -r" and you will get a unified diff of all your
    additions, modification and deletions. The diff will be stored in
    .patches/<patchname>.patch. It is in a form that allows direct
    application via patch(1) or, of course, via "patcher -i".

    Whenever you do "patcher -r" your .patches/<patchname>.patch file get's
    refreshed.

  Back out a patch

    To revoke your changes and go to the previous version, just enter
    "patcher -b". Patcher will make sure that you don't loose your changes
    by asking you to create a diff if something has changed since the last
    refresh. You may use -f (or --force) patcher to go back anyway.

    You can back out more than one patch by either specifying a number a
    patch name after -b.

  Re-Apply a patch

    With "patcher -n <patchname> -a" one can apply an already existing
    managed patch. A managed patch is a patch that already is stored in the
    .patches directory and is mentioned in the .patches/series file. Patcher
    tests if the patch would apply without problem and applies it. If the
    patch would be rejected, you can use -f (or --force) to apply the patch
    anyway.

    You can apply more than one patch by either specifying a number a patch
    name after -a.

  Importing external patches

    Sometimes you have an external patch. That's the opposite of a managed
    patch, the patch is not stored in the .patches directory. By importing
    it, it will become a managed patch.

    Import the patch simply with -i <filename>. You can use -p <num> to
    specify the directory level, similar to the -p<num> option of patch(1).
    But please keep in mind that we need a space between -p and the number.

    Normally only clean patches will be imported. To import a patch that
    creates rejects use -f (or --force). You'll see a list of files where
    the patch did not apply cleanly, fix the problems manually.

    Later you can use "patcher -r" to create a clean patch.

INSTALLATION
    Just place patcher somewhere in your path. That's all.

    For each project Patcher requires one special directory called
    ".patches". It will search for this directory. If it does not exist,
    patcher creates it automatically.

INTERNALS
    All work occurs with a single directory tree. All commands are invoked
    within the root of that tree (TODO: this can and should change). Patcher
    manages a "stack" of patches.

    Each patch is a changeset against the base tree plus the preceding
    patches.

    All patches are listed, in order, in the file ".patches/series". Patcher
    adds patches into this file, but never deletes entries. You can edit
    this file with a text editor, but please do only so if the patch you
    delete is currently not applied.

    Any currently applied patches is listed in the file ".patches/applied".
    The patcher manage this file, there is no need for you to ever edit this
    file manually.

    Each patch affects a number of files in the tree. These files are listed
    in a file list named ".patches/*.files". Patcher manages them. When you
    back out a patch, this file will deleted. Or, in other words, this file
    exists only for applied patches. It's only used by "patcher -r".

    Patches are placed into ".patches/*.patch" files. They are always
    unified diffs with -p1 as patchlevel. You can copy then anywhere, the
    patch(1) utility will read them without problems.

    Optionally you can put descriptions for the patches in files named
    ".patches/*.txt".

    So for a particular patch "my-first-patch" the following will exist:

    -   An entry "my-first-patch.patch" in ".patches/series".

    -   An entry "my-first-patch" in ".patches/applied" (if it's currently
        applied)

    -   A file ".patches/my-first-patch.files" which contains the names of
        the files which my-first-patch modifies, adds or removes

    -   A file ".patches/my-first-patch.patch", which is the context diff,
        basically the main output of patcher.

    -   Optionally a file ".patches/my-first-patch.txt" which contains the
        patch's changelog, description or whatever you put in there.

WALKTHROUGHT
    Let's start.

    Go into /usr/src/linux (or wherever).

    Now let's start with changing some source files:

            patcher -n my-patch kernel/sched.c

    OK, patcher copied kernel/sched.c to kernel/sched.c~my-patch for you,
    the program has also done some magic in the .patches directory, which
    won't be of interest to us now.

            Now edit kernel/sched.c a bit.

    Now we're ready to document the patch:

            Create .patches/my-patch.txt

    Now generate a patch:

            patcher -r

    This will generate ".patches/my-patch.patch". Take a look at this file.

    Now we remove our change to sched.c by going backwards:

            patcher -b

    Look at where we're now:

            patcher -s

    Now let's add another file to my-patch. First we re-apply the patch:

            patcher -a

    Now edit a second file:

            patcher kernel/printk.c

    Note that here we gave patcher a single argument, without command line
    options. This always tells patcher to add another file to the current
    patch.

            Edit kernel/printk.c

    Refresh my-patch:

            patcher -r

    Now start a second patch:

            patcher -n my-second-patch kernel/sched.c

    Here we have a filename in the command line for patcher, so we edit a
    file. But now we specified a patch name with -n. This told patcher to
    create a new patch. Now patcher manages two patches, "my-patch" and
    "my-second-patch".

            Edit kernel/sched.c, to make some changes for my-second-patch

    Generate my-second-patch:

            patcher -r

    Take a look in ".patches/my-second-patch.patch".

    Also note that "my-second-patch.patch" has been added to the series
    file. Whenever you manually begin a patch, it will automatically be put
    into the series file.

    In this way, the whole thing is stackable. If you have four patches
    applied, say "patch-1", "patch-2", "patch-3" and "patch-4", and if
    patch-2 and patch-4 both touch kernel/sched.c then you will have:

    kernel/sched.c~patch-2        Original copy, before patch-2

    kernel/sched.c~patch-4        Copy before patch-4. Contains changes from
                                  patch-2

    kernel/sched.c                Current working copy. Contains changes
                                  from patch-4.

    This means that your diff headers contain "~patch-name" in them, which
    is convenient documentation.

    To end our tour, we remove both patches:

            patcher -b
            patcher -b

    That's pretty much it, really.

SEE ALSO
    Andrew Morton's patch scripts at
    http://www.zip.com.au/~akpm/linux/patches/

    I stole the idea from him and even most of this documentation.

    At http://savannah.nongnu.org/projects/quilt/ you'll find Quilt. That's
    the successor of Andrew's original scripts. They do the same as patcher
    (and slightly more), but with tenthousand shell scripts.

AUTHOR
    Holger Schurig <holgerschurig usingthedomain gmx.de>