path: root/branch.c
diff options
authorConrad Irwin <>2011-08-20 21:49:48 (GMT)
committerJunio C Hamano <>2011-08-22 23:00:36 (GMT)
commit55c4a673070f40f2ef12d0be269e95f1df6825a9 (patch)
treef3167659326c1308f6dfe3600ec0b57200cef335 /branch.c
parent1be9d84b2ed18c2b2e2d6a459d2b6d48d5ab86e5 (diff)
Prevent force-updating of the current branch
"git branch -M <foo> <current-branch>" allows updating the current branch which HEAD points, without the necessary house-keeping that git reset normally does to make this operation sensible. It also leaves the reflog in a confusing state (you would be warned when trying to read it). "git checkout -B <current branch> <foo>" is also partly vulnerable to this bug; due to inconsistent pre-flight checks it would perform half of its task and then abort just before rewriting the branch. Again this manifested itself as the index file getting out-of-sync with HEAD. "git branch -f" already guarded against this problem, and aborts with a fatal error. Update "git branch -M", "git checkout -B" and "git branch -f" to share the same check before allowing a branch to be created. These prevent you from updating the current branch. We considered suggesting the use of "git reset" in the failure message but concluded that it was not possible to discern what the user was actually trying to do. Signed-off-by: Conrad Irwin <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'branch.c')
1 files changed, 24 insertions, 10 deletions
diff --git a/branch.c b/branch.c
index c0c865a..ff84b5b 100644
--- a/branch.c
+++ b/branch.c
@@ -135,6 +135,26 @@ static int setup_tracking(const char *new_ref, const char *orig_ref,
return 0;
+int validate_new_branchname(const char *name, struct strbuf *ref, int force)
+ const char *head;
+ unsigned char sha1[20];
+ if (strbuf_check_branch_ref(ref, name))
+ die("'%s' is not a valid branch name.", name);
+ if (!ref_exists(ref->buf))
+ return 0;
+ else if (!force)
+ die("A branch named '%s' already exists.", name);
+ head = resolve_ref("HEAD", sha1, 0, NULL);
+ if (!is_bare_repository() && head && !strcmp(head, ref->buf))
+ die("Cannot force update the current branch.");
+ return 1;
void create_branch(const char *head,
const char *name, const char *start_name,
int force, int reflog, enum branch_track track)
@@ -151,17 +171,11 @@ void create_branch(const char *head,
explicit_tracking = 1;
- if (strbuf_check_branch_ref(&ref, name))
- die("'%s' is not a valid branch name.", name);
- if (resolve_ref(ref.buf, sha1, 1, NULL)) {
- if (!force && track == BRANCH_TRACK_OVERRIDE)
+ if (validate_new_branchname(name, &ref, force || track == BRANCH_TRACK_OVERRIDE)) {
+ if (!force)
dont_change_ref = 1;
- else if (!force)
- die("A branch named '%s' already exists.", name);
- else if (!is_bare_repository() && head && !strcmp(head, name))
- die("Cannot force update the current branch.");
- forcing = 1;
+ else
+ forcing = 1;
real_ref = NULL;