@matheusbsbs / matheus-bagliano / commits / 31824d180d

branch: fix branch renaming not updating HEADs correctly

There are two bugs that sort of work together and cause problems. Let's start with one in replace_each_worktree_head_symref. Before fa099d2322 (worktree.c: kill parse_ref() in favor of refs_resolve_ref_unsafe() - 2017-04-24), this code looks like this: if (strcmp(oldref, worktrees[i]->head_ref)) continue; set_worktree_head_symref(...); After fa099d2322, it is possible that head_ref can be NULL. However, the updated code takes the wrong exit. In the error case (NULL head_ref), we should "continue;" to the next worktree. The updated code makes us _skip_ "continue;" and update HEAD anyway. The NULL head_ref is triggered by the second bug in add_head_info (in the same commit). With the flag RESOLVE_REF_READING, resolve_ref_unsafe() will abort if it cannot resolve the target ref. For orphan checkouts, HEAD always points to an unborned branch, resolving target ref will always fail. Now we have NULL head_ref. Now we always update HEAD. Correct the logic in replace_ function so that we don't accidentally update HEAD on error. As it turns out, correcting the logic bug above breaks branch renaming completely, thanks to the second bug. "git branch -[Mm]" does two steps (on a normal checkout, no orphan!): - rename the branch on disk (e.g. refs/heads/abc to refs/heads/def) - update HEAD if it points to the branch being renamed. At the second step, since the branch pointed to by HEAD (e.g. "abc") no longer exists on disk, we run into a temporary orphan checkout situation that has been just corrected to _not_ update HEAD. But we need to update HEAD since it's not actually an orphan checkout. We need to update HEAD to move out of that orphan state. Correct add_head_info(), remove RESOLVE_REF_READING flag. With the flag gone, we should always return good "head_ref" in orphan checkouts (either temporary or permanent). With good head_ref, things start to work again. Noticed-by: Nish Aravamudan <nish.aravamudan@canonical.com> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Nguyễn Thái Ngọc Duy committed Aug 24, 2017 at 17:41 UTC 31824d180d4f975e6b130cd9a33a9a0baef3d7ca

3 files changed +17 -3

branch.c

+3 -2

@@ -357,8 +357,9 @@ int replace_each_worktree_head_symref(const char *oldref, const char *newref,

357

358 if (worktrees[i]->is_detached)

359 continue;

360 - if (worktrees[i]->head_ref &&

361 - strcmp(oldref, worktrees[i]->head_ref))

360 + if (!worktrees[i]->head_ref)

361 + continue;

362 + if (strcmp(oldref, worktrees[i]->head_ref))

363 continue;

364

365 refs = get_worktree_ref_store(worktrees[i]);

t/t3200-branch.sh

+13

@@ -145,6 +145,19 @@ test_expect_success 'git branch -M baz bam should add entries to .git/logs/HEAD'

145 grep "^0\{40\}.*$msg$" .git/logs/HEAD

146 '

147

148 +test_expect_success 'git branch -M should leave orphaned HEAD alone' '

149 + git init orphan &&

150 + (

151 + cd orphan &&

152 + test_commit initial &&

153 + git checkout --orphan lonely &&

154 + grep lonely .git/HEAD &&

155 + test_path_is_missing .git/refs/head/lonely &&

156 + git branch -M master mistress &&

157 + grep lonely .git/HEAD

158 + )

159 +'

160 +

161 test_expect_success 'git branch -M baz bam should succeed when baz is checked out as linked working tree' '

162 git checkout master &&

163 git worktree add -b baz bazdir &&

worktree.c

+1 -1

@@ -29,7 +29,7 @@ static void add_head_info(struct worktree *wt)

30 target = refs_resolve_ref_unsafe(get_worktree_ref_store(wt),

31 "HEAD",

32 - RESOLVE_REF_READING,

32 + 0,

33 wt->head_sha1, &flags);

34 if (!target)

35 return;