[PATCH v2] contrib/subtree bugfix: Can't `add` annotated tag

cmd_add_commit() is passed FETCH_HEAD by cmd_add_repository, which is
then rev-parsed into an object ID. However, if the user is fetching a
tag rather than a branch HEAD, such as by executing:

$ git subtree add -P oldGit https://github.com/git/git.git tags/v1.8.0

The object ID is a tag and is never peeled, and the git commit-tree call
(line 561) slaps us in the face because it doesn't handle tag IDs.

Because peeling a committish ID doesn't do anything if it's already a
commit, fix by peeling[1] the object ID before assigning it to $rev, as
per the patch.

[*1*]: Via peel_committish(), from git:git-sh-setup.sh, pre-existing
dependency of git-subtree.

Reported-by: Kevin Cagle <redacted>
Helped-by: Junio C Hamano [off-list ref]
Signed-off-by: James Denholm <redacted>
---
I felt that defining revp would be a little more self-documenting than
using $rev^0.

 contrib/subtree/git-subtree.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index dc59a91..eefd720 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh

@@ -557,8 +557,9 @@ cmd_add_commit()
 		commit=$(add_squashed_msg "$rev" "$dir" |
 			 git commit-tree $tree $headp -p "$rev") || exit $?
 	else
+		revp=$(peel_committish "$rev")
 		commit=$(add_msg "$dir" "$headrev" "$rev" |
-			 git commit-tree $tree $headp -p "$rev") || exit $?
+			 git commit-tree $tree $headp -p "$revp") || exit $?
 	fi
 	git reset "$commit" || exit $?
 	

-- 
1.9.2