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diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
--- /dev/null
@@ -0,0 +1,712 @@
+#!/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: $cachedir"
+ mkdir -p "$cachedir/notree" || die "Can't create new cachedir: $cachedir/notree"
+ 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_miss()
+{
+ for oldrev in $*; do
+ if [ ! -r "$cachedir/$oldrev" ]; then
+ echo $oldrev
+ fi
+ done
+}
+
+check_parents()
+{
+ missed=$(cache_miss $*)
+ for miss in $missed; do
+ if [ ! -r "$cachedir/notree/$miss" ]; then
+ debug " incorrect order: $miss"
+ fi
+ done
+}
+
+set_notree()
+{
+ echo "1" > "$cachedir/notree/$1"
+}
+
+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" -o "$type" = "commit" ]
+ [ "$type" = "commit" ] && continue # ignore submodules
+ 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 --topo-order --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)\r"
+ 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"
+
+ check_parents $parents
+
+ # ugly. is there no better way to tell if this is a subtree
+ # vs. a mainline commit? Does it matter?
+ if [ -z $tree ]; then
+ set_notree $rev
+ if [ -n "$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_$command" "$@"