Add git-stash script

When my boss has something to show me and I have to update, for some
reason I am always in the middle of doing something else, and git pull
command refuses to work in such a case.

I wrote this little script to save the changes I made, perform the
update, and then come back to where I was, but on top of the updated
commit.

This is how you would use the script:

  $ git stash
  $ git pull
  $ git stash apply

[jc: with a few fixlets from the list]

Signed-off-by: Nanako Shiraishi <nanako3@bluebottle.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.gitignore

@@ -123,6 +123,7 @@ git-ssh-fetch
 git-ssh-pull
 git-ssh-push
 git-ssh-upload
+git-stash
 git-status
 git-stripspace
 git-submodule

Makefile

@@ -212,7 +212,8 @@ SCRIPT_SH = \
 	git-merge.sh git-merge-stupid.sh git-merge-octopus.sh \
 	git-merge-resolve.sh git-merge-ours.sh \
 	git-lost-found.sh git-quiltimport.sh git-submodule.sh \
-	git-filter-branch.sh
+	git-filter-branch.sh \
+	git-stash.sh
 
 SCRIPT_PERL = \
 	git-add--interactive.perl \

git-stash.sh

@@ -0,0 +1,160 @@
+#!/bin/sh
+# Copyright (c) 2007, Nanako Shiraishi
+
+USAGE='[ | list | show | apply | clear]'
+
+. git-sh-setup
+require_work_tree
+
+TMP="$GIT_DIR/.git-stash.$$"
+trap 'rm -f "$TMP-*"' 0
+
+ref_stash=refs/stash
+
+no_changes () {
+	git-diff-index --quiet --cached HEAD &&
+	git-diff-files --quiet
+}
+
+clear_stash () {
+	logfile="$GIT_DIR/logs/$ref_stash" &&
+	mkdir -p "$(dirname "$logfile")" &&
+	: >"$logfile"
+}
+
+save_stash () {
+	if no_changes
+	then
+		echo >&2 'No local changes to save'
+		exit 0
+	fi
+	test -f "$GIT_DIR/logs/$ref_stash" ||
+		clear_stash || die "Cannot initialize stash"
+
+	# state of the base commit
+	if b_commit=$(git-rev-parse --verify HEAD)
+	then
+		head=$(git-log --abbrev-commit --pretty=oneline -n 1 HEAD)
+	else
+		die "You do not have the initial commit yet"
+	fi
+
+	if branch=$(git-symbolic-ref -q HEAD)
+	then
+		branch=${branch#refs/heads/}
+	else
+		branch='(no branch)'
+	fi
+	msg=$(printf '%s: %s' "$branch" "$head")
+
+	# state of the index
+	i_tree=$(git-write-tree) &&
+	i_commit=$(printf 'index on %s' "$msg" |
+		git-commit-tree $i_tree -p $b_commit) ||
+		die "Cannot save the current index state"
+
+	# state of the working tree
+	w_tree=$( (
+		GIT_INDEX_FILE="$TMP-index" &&
+		export GIT_INDEX_FILE &&
+
+		rm -f "$TMP-index" &&
+		git-read-tree $i_tree &&
+		git-add -u &&
+		git-write-tree &&
+		rm -f "$TMP-index"
+	) ) ||
+		die "Cannot save the current worktree state"
+
+	# create the stash
+	w_commit=$(printf 'WIP on %s' "$msg" |
+		git-commit-tree $w_tree -p $b_commit -p $i_commit) ||
+		die "Cannot record working tree state"
+
+	git-update-ref -m "$msg" $ref_stash $w_commit ||
+		die "Cannot save the current status"
+	printf >&2 'Saved WIP on %s\n' "$msg"
+}
+
+list_stash () {
+	git-log --pretty=oneline -g "$@" $ref_stash |
+	sed -n -e 's/^[.0-9a-f]* refs\///p'
+}
+
+show_stash () {
+	flags=$(git-rev-parse --no-revs --flags "$@")
+	if test -z "$flags"
+	then
+		flags=--stat
+	fi
+	s=$(git-rev-parse --revs-only --no-flags --default $ref_stash "$@")
+
+	w_commit=$(git-rev-parse --verify "$s") &&
+	b_commit=$(git-rev-parse --verify "$s^") &&
+	git-diff $flags $b_commit $w_commit
+}
+
+apply_stash () {
+	git-diff-files --quiet ||
+		die 'Cannot restore on top of a dirty state'
+
+	# current index state
+	c_tree=$(git-write-tree) ||
+		die 'Cannot apply a stash in the middle of a merge'
+
+	s=$(git-rev-parse --revs-only --no-flags --default $ref_stash "$@") &&
+	w_tree=$(git-rev-parse --verify "$s:") &&
+	b_tree=$(git-rev-parse --verify "$s^:") ||
+		die "$*: no valid stashed state found"
+
+	eval "
+		GITHEAD_$w_tree='Stashed changes' &&
+		GITHEAD_$c_tree='Updated upstream' &&
+		GITHEAD_$b_tree='Version stash was based on' &&
+		export GITHEAD_$w_tree GITHEAD_$c_tree GITHEAD_$b_tree
+	"
+
+	if git-merge-recursive $b_tree -- $c_tree $w_tree
+	then
+		# No conflict
+		a="$TMP-added" &&
+		git-diff --cached --name-only --diff-filter=A $c_tree >"$a" &&
+		git-read-tree --reset $c_tree &&
+		git-update-index --add --stdin <"$a" ||
+			die "Cannot unstage modified files"
+		git-status
+		rm -f "$a"
+	else
+		# Merge conflict; keep the exit status from merge-recursive
+		exit
+	fi
+}
+
+# Main command set
+case "$1" in
+list)
+	shift
+	if test $# = 0
+	then
+		set x -n 10
+		shift
+	fi
+	list_stash "$@"
+	;;
+show)
+	shift
+	show_stash "$@"
+	;;
+apply)
+	shift
+	apply_stash "$@"
+	;;
+clear)
+	clear_stash
+	;;
+'')
+	save_stash && git-reset --hard
+	;;
+*)
+	usage
+esac