From 8b76e7bdd591776a4c5fad30d300435a21a7050f Mon Sep 17 00:00:00 2001
From: Tony Duckles <tony@nynim.org>
Date: Fri, 20 Aug 2010 00:38:29 -0500
Subject: [PATCH] Add git-subtree

---
 .gitconfig      |   1 +
 bin/git-subtree | 683 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 684 insertions(+)
 create mode 100755 bin/git-subtree

diff --git a/.gitconfig b/.gitconfig
index e020642..a81297e 100644
--- a/.gitconfig
+++ b/.gitconfig
@@ -19,6 +19,7 @@
 	lg = log -p
 	who = shortlog -s --
 	brdate = !git-brdate
+	subtree = !git-subtree
 
 [core]
 	filemode = true
diff --git a/bin/git-subtree b/bin/git-subtree
new file mode 100755
index 0000000..781eef3
--- /dev/null
+++ b/bin/git-subtree
@@ -0,0 +1,683 @@
+#!/bin/bash
+#
+# git-subtree.sh: split/join git repositories in subdirectories of this one
+#
+# Copyright (C) 2009 Avery Pennarun <apenwarr@gmail.com>
+#
+if [ $# -eq 0 ]; then
+    set -- -h
+fi
+OPTS_SPEC="\
+git subtree add   --prefix=<prefix> <commit>
+git subtree merge --prefix=<prefix> <commit>
+git subtree pull  --prefix=<prefix> <repository> <refspec...>
+git subtree push  --prefix=<prefix> <repository> <refspec...>
+git subtree split --prefix=<prefix> <commit...>
+--
+h,help        show the help
+q             quiet
+d             show debug messages
+P,prefix=     the name of the subdir to split out
+m,message=    use the given message as the commit message for the merge commit
+ options for 'split'
+annotate=     add a prefix to commit message of new commits
+b,branch=     create a new branch from the split subtree
+ignore-joins  ignore prior --rejoin commits
+onto=         try connecting new tree to an existing one
+rejoin        merge the new branch back into HEAD
+ options for 'add', 'merge', 'pull' and 'push'
+squash        merge subtree changes as a single commit
+"
+eval $(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)
+
+PATH=$PATH:$(git --exec-path)
+. git-sh-setup
+
+require_work_tree
+
+quiet=
+branch=
+debug=
+command=
+onto=
+rejoin=
+ignore_joins=
+annotate=
+squash=
+message=
+
+debug()
+{
+	if [ -n "$debug" ]; then
+		echo "$@" >&2
+	fi
+}
+
+say()
+{
+	if [ -z "$quiet" ]; then
+		echo "$@" >&2
+	fi
+}
+
+assert()
+{
+	if "$@"; then
+		:
+	else
+		die "assertion failed: " "$@"
+	fi
+}
+
+
+#echo "Options: $*"
+
+while [ $# -gt 0 ]; do
+	opt="$1"
+	shift
+	case "$opt" in
+		-q) quiet=1 ;;
+		-d) debug=1 ;;
+		--annotate) annotate="$1"; shift ;;
+		--no-annotate) annotate= ;;
+		-b) branch="$1"; shift ;;
+		-P) prefix="$1"; shift ;;
+		-m) message="$1"; shift ;;
+		--no-prefix) prefix= ;;
+		--onto) onto="$1"; shift ;;
+		--no-onto) onto= ;;
+		--rejoin) rejoin=1 ;;
+		--no-rejoin) rejoin= ;;
+		--ignore-joins) ignore_joins=1 ;;
+		--no-ignore-joins) ignore_joins= ;;
+		--squash) squash=1 ;;
+		--no-squash) squash= ;;
+		--) break ;;
+		*) die "Unexpected option: $opt" ;;
+	esac
+done
+
+command="$1"
+shift
+case "$command" in
+	add|merge|pull) default= ;;
+	split|push) default="--default HEAD" ;;
+	*) die "Unknown command '$command'" ;;
+esac
+
+if [ -z "$prefix" ]; then
+	die "You must provide the --prefix option."
+fi
+
+case "$command" in
+	add) [ -e "$prefix" ] && 
+		die "prefix '$prefix' already exists." ;;
+	*)   [ -e "$prefix" ] || 
+		die "'$prefix' does not exist; use 'git subtree add'" ;;
+esac
+
+dir="$(dirname "$prefix/.")"
+
+if [ "$command" != "pull" -a "$command" != "add" -a "$command" != "push" ]; then
+	revs=$(git rev-parse $default --revs-only "$@") || exit $?
+	dirs="$(git rev-parse --no-revs --no-flags "$@")" || exit $?
+	if [ -n "$dirs" ]; then
+		die "Error: Use --prefix instead of bare filenames."
+	fi
+fi
+
+debug "command: {$command}"
+debug "quiet: {$quiet}"
+debug "revs: {$revs}"
+debug "dir: {$dir}"
+debug "opts: {$*}"
+debug
+
+cache_setup()
+{
+	cachedir="$GIT_DIR/subtree-cache/$$"
+	rm -rf "$cachedir" || die "Can't delete old cachedir: $cachedir"
+	mkdir -p "$cachedir" || die "Can't create new cachedir: $cachedir"
+	debug "Using cachedir: $cachedir" >&2
+}
+
+cache_get()
+{
+	for oldrev in $*; do
+		if [ -r "$cachedir/$oldrev" ]; then
+			read newrev <"$cachedir/$oldrev"
+			echo $newrev
+		fi
+	done
+}
+
+cache_set()
+{
+	oldrev="$1"
+	newrev="$2"
+	if [ "$oldrev" != "latest_old" \
+	     -a "$oldrev" != "latest_new" \
+	     -a -e "$cachedir/$oldrev" ]; then
+		die "cache for $oldrev already exists!"
+	fi
+	echo "$newrev" >"$cachedir/$oldrev"
+}
+
+rev_exists()
+{
+	if git rev-parse "$1" >/dev/null 2>&1; then
+		return 0
+	else
+		return 1
+	fi
+}
+
+rev_is_descendant_of_branch()
+{
+	newrev="$1"
+	branch="$2"
+	branch_hash=$(git rev-parse $branch)
+	match=$(git rev-list -1 $branch_hash ^$newrev)
+
+	if [ -z "$match" ]; then
+		return 0
+	else
+		return 1
+	fi
+}
+
+# if a commit doesn't have a parent, this might not work.  But we only want
+# to remove the parent from the rev-list, and since it doesn't exist, it won't
+# be there anyway, so do nothing in that case.
+try_remove_previous()
+{
+	if rev_exists "$1^"; then
+		echo "^$1^"
+	fi
+}
+
+find_latest_squash()
+{
+	debug "Looking for latest squash ($dir)..."
+	dir="$1"
+	sq=
+	main=
+	sub=
+	git log --grep="^git-subtree-dir: $dir/*\$" \
+		--pretty=format:'START %H%n%s%n%n%b%nEND%n' HEAD |
+	while read a b junk; do
+		debug "$a $b $junk"
+		debug "{{$sq/$main/$sub}}"
+		case "$a" in
+			START) sq="$b" ;;
+			git-subtree-mainline:) main="$b" ;;
+			git-subtree-split:) sub="$b" ;;
+			END)
+				if [ -n "$sub" ]; then
+					if [ -n "$main" ]; then
+						# a rejoin commit?
+						# Pretend its sub was a squash.
+						sq="$sub"
+					fi
+					debug "Squash found: $sq $sub"
+					echo "$sq" "$sub"
+					break
+				fi
+				sq=
+				main=
+				sub=
+				;;
+		esac
+	done
+}
+
+find_existing_splits()
+{
+	debug "Looking for prior splits..."
+	dir="$1"
+	revs="$2"
+	main=
+	sub=
+	git log --grep="^git-subtree-dir: $dir/*\$" \
+		--pretty=format:'START %H%n%s%n%n%b%nEND%n' $revs |
+	while read a b junk; do
+		case "$a" in
+			START) sq="$b" ;;
+			git-subtree-mainline:) main="$b" ;;
+			git-subtree-split:) sub="$b" ;;
+			END)
+				debug "  Main is: '$main'"
+				if [ -z "$main" -a -n "$sub" ]; then
+					# squash commits refer to a subtree
+					debug "  Squash: $sq from $sub"
+					cache_set "$sq" "$sub"
+				fi
+				if [ -n "$main" -a -n "$sub" ]; then
+					debug "  Prior: $main -> $sub"
+					cache_set $main $sub
+					cache_set $sub $sub
+					try_remove_previous "$main"
+					try_remove_previous "$sub"
+				fi
+				main=
+				sub=
+				;;
+		esac
+	done
+}
+
+copy_commit()
+{
+	# We're going to set some environment vars here, so
+	# do it in a subshell to get rid of them safely later
+	debug copy_commit "{$1}" "{$2}" "{$3}"
+	git log -1 --pretty=format:'%an%n%ae%n%ad%n%cn%n%ce%n%cd%n%s%n%n%b' "$1" |
+	(
+		read GIT_AUTHOR_NAME
+		read GIT_AUTHOR_EMAIL
+		read GIT_AUTHOR_DATE
+		read GIT_COMMITTER_NAME
+		read GIT_COMMITTER_EMAIL
+		read GIT_COMMITTER_DATE
+		export  GIT_AUTHOR_NAME \
+			GIT_AUTHOR_EMAIL \
+			GIT_AUTHOR_DATE \
+			GIT_COMMITTER_NAME \
+			GIT_COMMITTER_EMAIL \
+			GIT_COMMITTER_DATE
+		(echo -n "$annotate"; cat ) |
+		git commit-tree "$2" $3  # reads the rest of stdin
+	) || die "Can't copy commit $1"
+}
+
+add_msg()
+{
+	dir="$1"
+	latest_old="$2"
+	latest_new="$3"
+	if [ -n "$message" ]; then
+		commit_message="$message"
+	else
+		commit_message="Add '$dir/' from commit '$latest_new'"
+	fi
+	cat <<-EOF
+		$commit_message
+		
+		git-subtree-dir: $dir
+		git-subtree-mainline: $latest_old
+		git-subtree-split: $latest_new
+	EOF
+}
+
+add_squashed_msg()
+{
+	if [ -n "$message" ]; then
+		echo "$message"
+	else
+		echo "Merge commit '$1' as '$2'"
+	fi
+}
+
+rejoin_msg()
+{
+	dir="$1"
+	latest_old="$2"
+	latest_new="$3"
+	if [ -n "$message" ]; then
+		commit_message="$message"
+	else
+		commit_message="Split '$dir/' into commit '$latest_new'"
+	fi
+	cat <<-EOF
+		$commit_message
+		
+		git-subtree-dir: $dir
+		git-subtree-mainline: $latest_old
+		git-subtree-split: $latest_new
+	EOF
+}
+
+squash_msg()
+{
+	dir="$1"
+	oldsub="$2"
+	newsub="$3"
+	newsub_short=$(git rev-parse --short "$newsub")
+	
+	if [ -n "$oldsub" ]; then
+		oldsub_short=$(git rev-parse --short "$oldsub")
+		echo "Squashed '$dir/' changes from $oldsub_short..$newsub_short"
+		echo
+		git log --pretty=tformat:'%h %s' "$oldsub..$newsub"
+		git log --pretty=tformat:'REVERT: %h %s' "$newsub..$oldsub"
+	else
+		echo "Squashed '$dir/' content from commit $newsub_short"
+	fi
+	
+	echo
+	echo "git-subtree-dir: $dir"
+	echo "git-subtree-split: $newsub"
+}
+
+toptree_for_commit()
+{
+	commit="$1"
+	git log -1 --pretty=format:'%T' "$commit" -- || exit $?
+}
+
+subtree_for_commit()
+{
+	commit="$1"
+	dir="$2"
+	git ls-tree "$commit" -- "$dir" |
+	while read mode type tree name; do
+		assert [ "$name" = "$dir" ]
+		assert [ "$type" = "tree" ]
+		echo $tree
+		break
+	done
+}
+
+tree_changed()
+{
+	tree=$1
+	shift
+	if [ $# -ne 1 ]; then
+		return 0   # weird parents, consider it changed
+	else
+		ptree=$(toptree_for_commit $1)
+		if [ "$ptree" != "$tree" ]; then
+			return 0   # changed
+		else
+			return 1   # not changed
+		fi
+	fi
+}
+
+new_squash_commit()
+{
+	old="$1"
+	oldsub="$2"
+	newsub="$3"
+	tree=$(toptree_for_commit $newsub) || exit $?
+	if [ -n "$old" ]; then
+		squash_msg "$dir" "$oldsub" "$newsub" | 
+			git commit-tree "$tree" -p "$old" || exit $?
+	else
+		squash_msg "$dir" "" "$newsub" |
+			git commit-tree "$tree" || exit $?
+	fi
+}
+
+copy_or_skip()
+{
+	rev="$1"
+	tree="$2"
+	newparents="$3"
+	assert [ -n "$tree" ]
+
+	identical=
+	nonidentical=
+	p=
+	gotparents=
+	for parent in $newparents; do
+		ptree=$(toptree_for_commit $parent) || exit $?
+		[ -z "$ptree" ] && continue
+		if [ "$ptree" = "$tree" ]; then
+			# an identical parent could be used in place of this rev.
+			identical="$parent"
+		else
+			nonidentical="$parent"
+		fi
+		
+		# sometimes both old parents map to the same newparent;
+		# eliminate duplicates
+		is_new=1
+		for gp in $gotparents; do
+			if [ "$gp" = "$parent" ]; then
+				is_new=
+				break
+			fi
+		done
+		if [ -n "$is_new" ]; then
+			gotparents="$gotparents $parent"
+			p="$p -p $parent"
+		fi
+	done
+	
+	if [ -n "$identical" ]; then
+		echo $identical
+	else
+		copy_commit $rev $tree "$p" || exit $?
+	fi
+}
+
+ensure_clean()
+{
+	if ! git diff-index HEAD --exit-code --quiet 2>&1; then
+		die "Working tree has modifications.  Cannot add."
+	fi
+	if ! git diff-index --cached HEAD --exit-code --quiet 2>&1; then
+		die "Index has modifications.  Cannot add."
+	fi
+}
+
+cmd_add()
+{
+	if [ -e "$dir" ]; then
+		die "'$dir' already exists.  Cannot add."
+	fi
+
+	ensure_clean
+	
+	if [ $# -eq 1 ]; then
+		"cmd_add_commit" "$@"
+	elif [ $# -eq 2 ]; then
+		"cmd_add_repository" "$@"
+	else
+	    say "error: parameters were '$@'"
+	    die "Provide either a refspec or a repository and refspec."
+	fi
+}
+
+cmd_add_repository()
+{
+	echo "git fetch" "$@"
+	repository=$1
+	refspec=$2
+	git fetch "$@" || exit $?
+	revs=FETCH_HEAD
+	set -- $revs
+	cmd_add_commit "$@"
+}
+
+cmd_add_commit()
+{
+	revs=$(git rev-parse $default --revs-only "$@") || exit $?
+	set -- $revs
+	rev="$1"
+	
+	debug "Adding $dir as '$rev'..."
+	git read-tree --prefix="$dir" $rev || exit $?
+	git checkout -- "$dir" || exit $?
+	tree=$(git write-tree) || exit $?
+	
+	headrev=$(git rev-parse HEAD) || exit $?
+	if [ -n "$headrev" -a "$headrev" != "$rev" ]; then
+		headp="-p $headrev"
+	else
+		headp=
+	fi
+	
+	if [ -n "$squash" ]; then
+		rev=$(new_squash_commit "" "" "$rev") || exit $?
+		commit=$(add_squashed_msg "$rev" "$dir" |
+			 git commit-tree $tree $headp -p "$rev") || exit $?
+	else
+		commit=$(add_msg "$dir" "$headrev" "$rev" |
+			 git commit-tree $tree $headp -p "$rev") || exit $?
+	fi
+	git reset "$commit" || exit $?
+	
+	say "Added dir '$dir'"
+}
+
+cmd_split()
+{
+	debug "Splitting $dir..."
+	cache_setup || exit $?
+	
+	if [ -n "$onto" ]; then
+		debug "Reading history for --onto=$onto..."
+		git rev-list $onto |
+		while read rev; do
+			# the 'onto' history is already just the subdir, so
+			# any parent we find there can be used verbatim
+			debug "  cache: $rev"
+			cache_set $rev $rev
+		done
+	fi
+	
+	if [ -n "$ignore_joins" ]; then
+		unrevs=
+	else
+		unrevs="$(find_existing_splits "$dir" "$revs")"
+	fi
+	
+	# We can't restrict rev-list to only $dir here, because some of our
+	# parents have the $dir contents the root, and those won't match.
+	# (and rev-list --follow doesn't seem to solve this)
+	grl='git rev-list --reverse --parents $revs $unrevs'
+	revmax=$(eval "$grl" | wc -l)
+	revcount=0
+	createcount=0
+	eval "$grl" |
+	while read rev parents; do
+		revcount=$(($revcount + 1))
+		say -n "$revcount/$revmax ($createcount)
"
+		debug "Processing commit: $rev"
+		exists=$(cache_get $rev)
+		if [ -n "$exists" ]; then
+			debug "  prior: $exists"
+			continue
+		fi
+		createcount=$(($createcount + 1))
+		debug "  parents: $parents"
+		newparents=$(cache_get $parents)
+		debug "  newparents: $newparents"
+		
+		tree=$(subtree_for_commit $rev "$dir")
+		debug "  tree is: $tree"
+		
+		# ugly.  is there no better way to tell if this is a subtree
+		# vs. a mainline commit?  Does it matter?
+		if [ -z $tree ]; then
+			if [ -n "$newparents" ]; then
+				cache_set $rev $rev
+			fi
+			continue
+		fi
+
+		newrev=$(copy_or_skip "$rev" "$tree" "$newparents") || exit $?
+		debug "  newrev is: $newrev"
+		cache_set $rev $newrev
+		cache_set latest_new $newrev
+		cache_set latest_old $rev
+	done || exit $?
+	latest_new=$(cache_get latest_new)
+	if [ -z "$latest_new" ]; then
+		die "No new revisions were found"
+	fi
+	
+	if [ -n "$rejoin" ]; then
+		debug "Merging split branch into HEAD..."
+		latest_old=$(cache_get latest_old)
+		git merge -s ours \
+			-m "$(rejoin_msg $dir $latest_old $latest_new)" \
+			$latest_new >&2 || exit $?
+	fi
+	if [ -n "$branch" ]; then
+		if rev_exists "refs/heads/$branch"; then
+			if ! rev_is_descendant_of_branch $latest_new $branch; then
+				die "Branch '$branch' is not an ancestor of commit '$latest_new'."
+			fi
+			action='Updated'
+		else
+			action='Created'
+		fi
+		git update-ref -m 'subtree split' "refs/heads/$branch" $latest_new || exit $?
+		say "$action branch '$branch'"
+	fi
+	echo $latest_new
+	exit 0
+}
+
+cmd_merge()
+{
+	revs=$(git rev-parse $default --revs-only "$@") || exit $?
+	ensure_clean
+	
+	set -- $revs
+	if [ $# -ne 1 ]; then
+		die "You must provide exactly one revision.  Got: '$revs'"
+	fi
+	rev="$1"
+	
+	if [ -n "$squash" ]; then
+		first_split="$(find_latest_squash "$dir")"
+		if [ -z "$first_split" ]; then
+			die "Can't squash-merge: '$dir' was never added."
+		fi
+		set $first_split
+		old=$1
+		sub=$2
+		if [ "$sub" = "$rev" ]; then
+			say "Subtree is already at commit $rev."
+			exit 0
+		fi
+		new=$(new_squash_commit "$old" "$sub" "$rev") || exit $?
+		debug "New squash commit: $new"
+		rev="$new"
+	fi
+
+	version=$(git version)
+	if [ "$version" \< "git version 1.7" ]; then
+		if [ -n "$message" ]; then
+			git merge -s subtree --message="$message" $rev
+		else
+			git merge -s subtree $rev
+		fi
+	else
+		if [ -n "$message" ]; then
+			git merge -Xsubtree="$prefix" --message="$message" $rev
+		else
+			git merge -Xsubtree="$prefix" $rev
+		fi
+	fi
+}
+
+cmd_pull()
+{
+	ensure_clean
+	git fetch "$@" || exit $?
+	revs=FETCH_HEAD
+	set -- $revs
+	cmd_merge "$@"
+}
+
+cmd_push()
+{
+	if [ $# -ne 2 ]; then
+	    die "You must provide <repository> <refspec>"
+	fi
+	if [ -e "$dir" ]; then
+	    repository=$1
+	    refspec=$2
+	    echo "git push using: " $repository $refspec
+	    git push $repository $(git subtree split --prefix=$prefix):refs/heads/$refspec
+	else
+	    die "'$dir' must already exist. Try 'git subtree add'."
+	fi
+}
+
+"cmd_$command" "$@"
-- 
2.45.2