[TOY PATCH] git-resurrect: find traces of a branch name and resurrect it

[Thomas Rast <trast@student.ethz.ch>]

Add a tool 'git resurrect <branch>...' that tries to find traces of
each <branch> in the HEAD reflog and, optionally, all merge commits in
the repository.  It can then resurrect the branch, pointing it at the
most recent of all candidate commits found.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
---

So here's a slightly more polished version so gmane can keep it
forever.  Thanks for the sed trick!  I was too lazy to add more
options, but at least there's a "fast" and a "complete" mode.



 Makefile         |    1 +
 git-resurrect.sh |  109 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+), 0 deletions(-)
 create mode 100755 git-resurrect.sh

diff --git a/Makefile b/Makefile
index 2b873fa..87cb539 100644
--- a/Makefile
+++ b/Makefile
@@ -260,6 +260,7 @@ SCRIPT_SH += git-merge-resolve.sh
 SCRIPT_SH += git-mergetool.sh
 SCRIPT_SH += git-parse-remote.sh
 SCRIPT_SH += git-pull.sh
+SCRIPT_SH += git-resurrect.sh
 SCRIPT_SH += git-quiltimport.sh
 SCRIPT_SH += git-rebase--interactive.sh
 SCRIPT_SH += git-rebase.sh
diff --git a/git-resurrect.sh b/git-resurrect.sh
new file mode 100755
index 0000000..6d5a0c7
--- /dev/null
+++ b/git-resurrect.sh
@@ -0,0 +1,109 @@
+#!/bin/sh
+
+USAGE="git resurrect [-m | --merges] [-n | --dry-run] <name>..."
+LONG_USAGE="git-resurrect attempts to find traces of a branch tip called <name>,
+and tries to resurrect it.  Currently, the reflog is searched for
+checkout and merge messages.  With --merges, the history of all refs
+is scanned for merge commit subjects, which is rather slow but allows
+you to resurrect other people's topic branches."
+
+. git-sh-setup
+cd_to_toplevel
+
+OPTIONS_SPEC="\
+git resurrect [-m | --merges] [-n | --dry-run] <name>...
+--
+m,merges             also scan merges (slow)
+n,dry-run            don't recreate the branch"
+
+test "$#" = 0 && usage
+
+eval "$(echo "$OPTIONS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)"
+
+search_reflog () {
+        sed -n 's~^\([^ ]*\) .*\tcheckout: moving from '"$1"' .*~\1~p' \
+                < .git/logs/HEAD
+}
+
+search_reflog_merges () {
+        sed -n 's~^[^ ]* \([^ ]*\) .*\tmerge '"$1"':~\1~p' \
+                < .git/logs/HEAD
+}
+
+search_merges () {
+	git rev-list --pretty=tformat:"%h %p:%s" --all |
+	grep "Merge branch.*'$branch'.*into" |
+	while read sha rest; do
+		parents="$(echo "$rest" | cut -d: -f1)"
+		case "$parents" in
+		    *' '*' '*)
+			warn "$branch took part in octopus merge $sha"
+			warn "check manually!"
+			;;
+		    *' '*)
+			echo "$parents" | cut -d' ' -f2
+			;;
+		esac
+	done
+}
+
+search_merge_targets () {
+	git rev-list --pretty=tformat:"%h %s" --all |
+	grep "Merge branch '[^']*' into $branch$" |
+	cut -d' ' -f1
+}
+
+dry_run=
+scan_merges=
+
+while test "$#" != 0; do
+	case "$1" in
+	    -n|--dry-run)
+		dry_run=t
+		;;
+	    -m|--merges)
+		scan_merges=t
+		;;
+	    --)
+		shift
+		break
+		;;
+	    *)
+		usage
+		;;
+	esac
+	shift
+done
+
+for branch in "$@"; do
+	candidates="$(search_reflog $1; search_reflog_merges $1)"
+	if test ! -z "$scan_merges"; then
+		candidates="$candidates $(search_merges $1; search_merge_targets $1)"
+	fi
+
+	candidates="$(git rev-parse $candidates | sort -u)"
+
+	if test -z "$candidates"; then
+		echo "** No candidates for $branch found **"
+		test -z "$scan_merges" && echo "(maybe try again with -m)"
+	else
+		echo "** Candidates for $branch **"
+		for cmt in $candidates; do
+			git --no-pager log --pretty=oneline --abbrev-commit -1 $cmt
+		done
+
+		newest="$(git rev-list -1 $candidates)"
+		if test ! -z "$dry_run"; then
+			printf "Most recent: "
+			git --no-pager log -1 --pretty=tformat:"%h %s" $newest
+		elif ! git rev-parse --verify --quiet $branch >/dev/null; then
+			printf "** Restoring $branch to "
+			git --no-pager log -1 --pretty=tformat:"%h %s" $newest
+			git branch $branch $newest
+		else
+			printf "Most recent: "
+			git --no-pager log -1 --pretty=tformat:"%h %s" $newest
+			echo "** $branch already exists, doing nothing"
+		fi
+	fi
+done
-- 
1.6.1.320.gd5dca.dirty