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#!/usr/bin/env bash
#
# git-clone-subset - clones a subset of a git repository
#
# Copyright (C) 2012 Rodrigo Silva (MestreLion) <linux@rodrigosilva.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not see <http://www.gnu.org/licenses/gpl.html>
#
# Uses git clone and git filter-branch to remove from the clone all files but
# the ones requested, along with their associated commit history.
usage() {
cat <<- USAGE
Usage: $myname [options] <repository> <destination-dir> <pattern>
USAGE
if [[ "$1" ]] ; then
cat >&2 <<- USAGE
Try '$myname --help' for more information.
USAGE
exit 1
fi
cat <<-USAGE
Clones a <repository> into a <destination-dir> and prune from history
all files except the ones matching <pattern> by running on the clone:
git filter-branch --prune-empty --tree-filter 'git rm ...' -- --all
This effectively creates a clone with a subset of files (and history)
of the original repository. The original repository is not modified.
Useful for creating a new repository out of a set of files from another
repository, migrating (only) their associated history. Very similar to:
git filter-branch --subdirectory-filter
But $myname works on a path pattern instead of just a single directory.
Options:
-h, --help
show this page.
<repository>
URL or local path to the git repository to be cloned.
<destination-dir>
Directory to create the clone. Same rules for git-clone applies: it
will be created if it does not exist and it must be empty otherwise.
But, unlike git-clone, this argument is not optional: git-clone uses
several rules to determine the "friendly" basename of a cloned repo,
and $myname will not risk parse its output, let alone
predict the chosen name.
<pattern>
Glob pattern to match the desired files/dirs. It will be ultimately
evaluated by a call to bash, NOT git or sh, using extended glob
'!(<pattern>)' rule. Quote it or escape it on command line, so it
does not get evaluated prematurely by your current shell. Only a
single pattern is allowed: if more are required, use extglob's "|"
syntax. Globs will be evaluated with bash's shopt dotglob set, so
beware. Patterns should not contain spaces or special chars like
" ' \$ ( ) { } \`, not even quoted or escaped, since that might
interfere with the !() syntax after pattern expansion.
Pattern Examples:
"*.png"
"*.png|*icon*"
"*.h|src/|lib"
Limitations:
- Renames are NOT followed. As a workaround, list the rename history with
'git log --follow --name-status --format='%H' -- file | grep "^[RAD]"'
and include all multiple names of a file in the pattern, as in
"current_name|old_name|initial_name". As a side effect, if a different
file has taken place of an old name, it will be preserved too, and
there is no way around this using this tool.
- There is no (easy) way to keep some files in a dir: using 'dir/foo*'
as pattern will not work. So keep the whole dir and remove files
afterwards, using git filter-branch and a (quite complex) combination
of cloning, remote add, rebase, etc.
- Pattern matching is quite limited, and many of bash's escaping and
quoting does not work properly when pattern is expanded inside !().
Copyright (C) 2013 Rodrigo Silva (MestreLion) <linux@rodrigosilva.com>
License: GPLv3 or later. See <http://www.gnu.org/licenses/gpl.html>
USAGE
exit 0
}
# Helper functions
myname="${0##*/}"
argerr() { printf "%s: %s\n" "${0##*/}" "${1:-error}" >&2 ; usage 1 ; }
invalid() { argerr "invalid option: $1" ; }
missing() { argerr "missing ${2:+$2 }operand${1:+ from $1}." ; }
# Argument handling
for arg in "$@"; do case "$arg" in -h|--help) usage ;; esac; done
repo=$1
dir=$2
pattern=$3
[[ "$repo" ]] || missing "" "<repository>"
[[ "$dir" ]] || missing "" "<destination-dir>"
[[ "$pattern" ]] || missing "" "<pattern>"
(($# > 3)) && argerr "too many arguments: $4"
# Clone the repo and enter it
git clone --no-hardlinks "$repo" "$dir" && cd "$dir" &&
# Remove remotes (a clone is meant to be a different repository)
while read -r remote; do
git remote rm "$remote" || break
done < <(git remote) &&
# The heart of the script
git filter-branch --prune-empty --tree-filter \
"bash -O dotglob -O extglob -c 'git rm -rf --ignore-unmatch -- !($pattern)'" \
-- --all &&
# fix a bug in filter-branch where empty root commits are not removed
# even with --prune-empty. First we loop each root commit
while read -r root; do
# Test if it's an non-empty commit
if [[ "$(git ls-tree "$root")" ]]; then continue; fi
# Now "remove" it by deleting its child's parent reference
git filter-branch --force --parent-filter "sed 's/-p $root//'" -- --all
done < <(git rev-list --max-parents=0 HEAD) &&
# Delete backups and the reflog, not needed in a clone
if [[ -e .git/refs/original/ ]] ; then
git "for-each-ref" --format="%(refname)" refs/original/ |
xargs -n 1 git update-ref -d
fi &&
git reflog expire --expire=now --all &&
git gc --prune=now
|
