fast-import: don't allow to tag empty branch

'reset' command makes fast-import start a branch from scratch. It's name
is kept in lookup table but it's sha1 is null_sha1 (special value).
'tag' command can be used to tag a branch by it's name. lookup_branch()
is used it that case and it doesn't check for null_sha1. So fast-import
writes a tag for null_sha1 object instead of giving a error.

Add a check to deny tagging an empty branch and add a corresponding test.

Signed-off-by: Dmitry Ivankov <divanorama@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/fast-import.c b/fast-import.c
index 742e7da6b8b58dd0803d89c6ad6c59589274a31b..c44cc11fd7994fd4591bc7e445777da376d481d1 100644 (file)
--- a/fast-import.c
+++ b/fast-import.c
@@ -2717,6 +2717,8 @@ static void parse_new_tag(void)
        from = strchr(command_buf.buf, ' ') + 1;
        s = lookup_branch(from);
        if (s) {
+               if (is_null_sha1(s->sha1))
+                       die("Can't tag an empty branch.");
                hashcpy(sha1, s->sha1);
                type = OBJ_COMMIT;
        } else if (*from == ':') {

diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index 1a6c06631c1c2a8fc29b66c9265541b54e8a9715..0b97d7aab92b1531de04fe5cd43402940efc0f3e 100755 (executable)
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -820,6 +820,18 @@ test_expect_success \
        'test 1 = `git rev-list J | wc -l` &&
         test 0 = `git ls-tree J | wc -l`'
 
+cat >input <<INPUT_END
+reset refs/heads/J2
+
+tag wrong_tag
+from refs/heads/J2
+data <<EOF
+Tag branch that was reset.
+EOF
+INPUT_END
+test_expect_success \
+       'J: tag must fail on empty branch' \
+       'test_must_fail git fast-import <input'
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