subtree: push: allow specifying a local rev other than HEAD

'git subtree split' lets you specify a rev other than HEAD.  'git push'
lets you specify a mapping between a local thing and a remot ref.  So
smash those together, and have 'git subtree push' let you specify which
local thing to run split on and push the result of that split to the
remote ref.

Signed-off-by: Luke Shumaker <lukeshu@datawire.io>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 17 insertions, 7 deletions

diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index 431214a1d3..9e4d9a0619 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -27,7 +27,7 @@ git subtree add   --prefix=<prefix> <repository> <ref>
 git subtree merge --prefix=<prefix> <commit>
 git subtree split --prefix=<prefix> [<commit>]
 git subtree pull  --prefix=<prefix> <repository> <ref>
-git subtree push  --prefix=<prefix> <repository> <ref>
+git subtree push  --prefix=<prefix> <repository> <refspec>
 --
 h,help        show the help
 q             quiet
@@ -952,20 +952,30 @@ cmd_pull () {
 	cmd_merge FETCH_HEAD
 }
 
-# Usage: cmd_push REPOSITORY REMOTEREF
+# Usage: cmd_push REPOSITORY [+][LOCALREV:]REMOTEREF
 cmd_push () {
 	if test $# -ne 2
 	then
-		die "You must provide <repository> <ref>"
+		die "You must provide <repository> <refspec>"
 	fi
-	ensure_valid_ref_format "$2"
 	if test -e "$dir"
 	then
 		repository=$1
-		refspec=$2
+		refspec=${2#+}
+		remoteref=${refspec#*:}
+		if test "$remoteref" = "$refspec"
+		then
+			localrevname_presplit=HEAD
+		else
+			localrevname_presplit=${refspec%%:*}
+		fi
+		ensure_valid_ref_format "$remoteref"
+		localrev_presplit=$(git rev-parse -q --verify "$localrevname_presplit^{commit}") ||
+			die "'$localrevname_presplit' does not refer to a commit"
+
 		echo "git push using: " "$repository" "$refspec"
-		localrev=$(cmd_split) || die
-		git push "$repository" "$localrev":"refs/heads/$refspec"
+		localrev=$(cmd_split "$localrev_presplit") || die
+		git push "$repository" "$localrev":"refs/heads/$remoteref"
 	else
 		die "'$dir' must already exist. Try 'git subtree add'."
 	fi