Re: git filter-branch doesn't dereference annotated tags

From

Grégory Pakosz <gpakosz@visionobjects.com>

Date

Jan 2, 2013, 22:03 UTC

Message-ID

<CAC_01E2iHgNvh5PnBh3TcNKr2pLazZwRojVK9ksaE3x0a1QHmQ@mail.gmail.com>

In-Reply-To

<7vk3rwaa3r.fsf@alter.siamese.dyndns.org>

> I was wondering if it should be
>
>         sha1=$(git rev-parse --verify "$ref")
>
> or something that does not dereference a tag at all.
>
> The way I read what that loop seems to want to do is:
>
>         Read each refname that was given originally from the file
>         $tempdir/heads, find out the object it used to refer to and
>         have it in $sha1, find out what new object the object was
>         rewritten to and have it in $rewritten, and:
>
>         (1) if the rewrite left the object unchanged, do nothing but
>             warn users just in case this was a mistake;
>         (2) if the rewrite told us to remove it, then delete the
>             ref; or
>         (3) if the rewrite gave us a new object, replace the ref to
>             point to that new one.
>
>         And in the latter two cases, save the original one in
>         $orig_namespace so that the user can choose to recover if
>         this filter-branch was done by mistake.
>
> So I do not think unwraping the ref at that point makes any sense,
> unless it is not prepared to handle annotated tags at all by
> unwrapping tags too early.
>
> What am I missing?
>

My initial questions and patching suggestions are based on git
1.7.10.4 behavior.
However, playing with git HEAD exhibits a slightly different behavior:
it breaks when invoking git mktag line 459 (introduced by
1bf6551e42c79a594689a356a9b14759d55f3cf5):
  error: char7: could not get SHA1 hash
  fatal: invalid tag signature file
  Could not create new tag object for tag-a

I tested the patch doesn't break t7003. What do you think?

Gregory

From 2cb9d5bc605cc2f2d8a6603b6a06657516959aa6 Mon Sep 17 00:00:00 2001
From: Gregory Pakosz <gpakosz@visionobjects.com>
Date: Wed, 2 Jan 2013 23:02:03 +0100
Subject: [PATCH] git-filter-branch: allow deletion of tags when referenced
 commit gets rewritten to nothing

---
 git-filter-branch.sh | 61 ++++++++++++++++++++++++++++------------------------
 1 file changed, 33 insertions(+), 28 deletions(-)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 5314249..2e8569c 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -436,36 +436,41 @@ if [ "$filter_tag_name" ]; then
 
 		[ -f "../map/$sha1" ] || continue
 		new_sha1="$(cat "../map/$sha1")"
-		GIT_COMMIT="$sha1"
-		export GIT_COMMIT
-		new_ref="$(echo "$ref" | eval "$filter_tag_name")" ||
-			die "tag name filter failed: $filter_tag_name"
-
-		echo "$ref -> $new_ref ($sha1 -> $new_sha1)"
-
-		if [ "$type" = "tag" ]; then
-			new_sha1=$( ( printf 'object %s\ntype commit\ntag %s\n' \
-						"$new_sha1" "$new_ref"
-				git cat-file tag "$ref" |
-				sed -n \
-				    -e '1,/^$/{
-					  /^object /d
-					  /^type /d
-					  /^tag /d
-					}' \
-				    -e '/^-----BEGIN PGP SIGNATURE-----/q' \
-				    -e 'p' ) |
-				git mktag) ||
-				die "Could not create new tag object for $ref"
-			if git cat-file tag "$ref" | \
-			   sane_grep '^-----BEGIN PGP SIGNATURE-----' >/dev/null 2>&1
-			then
-				warn "gpg signature stripped from tag object $sha1t"
+		if [ -n "$new_sha1" ]; then
+			GIT_COMMIT="$sha1"
+			export GIT_COMMIT
+			new_ref="$(echo "$ref" | eval "$filter_tag_name")" ||
+				die "tag name filter failed: $filter_tag_name"
+
+			echo "$ref -> $new_ref ($sha1 -> $new_sha1)"
+
+			if [ "$type" = "tag" ]; then
+				new_sha1=$( ( printf 'object %s\ntype commit\ntag %s\n' \
+							"$new_sha1" "$new_ref"
+					git cat-file tag "$ref" |
+					sed -n \
+							-e '1,/^$/{
+							/^object /d
+							/^type /d
+							/^tag /d
+						}' \
+							-e '/^-----BEGIN PGP SIGNATURE-----/q' \
+							-e 'p' ) |
+					git mktag) ||
+					die "Could not create new tag object for $ref"
+				if git cat-file tag "$ref" | \
+					sane_grep '^-----BEGIN PGP SIGNATURE-----' >/dev/null 2>&1
+				then
+					warn "gpg signature stripped from tag object $sha1t"
+				fi
 			fi
-		fi
 
-		git update-ref "refs/tags/$new_ref" "$new_sha1" ||
-			die "Could not write tag $new_ref"
+			git update-ref "refs/tags/$new_ref" "$new_sha1" ||
+				die "Could not write tag $new_ref"
+		else
+			git update-ref -d "refs/tags/$ref" "$sha1t" ||
+				die "Could not delete tag $ref"
+		fi
 	done
 fi
 

-- 
1.8.0.1