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rebase -i: stop overwriting ORIG_HEAD buffer

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After rebasing, ORIG_HEAD is supposed to point to the old HEAD of the
rebased branch.  The code used find_unique_abbrev() to obtain the
object name of the old HEAD and wrote to both
.git/rebase-merge/orig-head (used by `rebase --abort` to go back to
the previous state) and to ORIG_HEAD.  The buffer find_unique_abbrev()
gives back is volatile, unfortunately, and was overwritten after the
former file is written but before ORIG_FILE is written, leaving an
incorrect object name in it.

Avoid relying on the volatile buffer of find_unique_abbrev(), and
instead supply our own buffer to keep the object name.

I think that all of the users of head_hash should actually be using
opts->orig_head instead as passing a string rather than a struct
object_id around is a hang over from the scripted implementation. This
patch just fixes the immediate bug and adds a regression test based on
Caspar's reproduction example[1]. The users will be converted to use
struct object_id and head_hash removed in the next few commits.

[1] https://lore.kernel.org/git/CAFzd1+7PDg2PZgKw7U0kdepdYuoML9wSN4kofmB_-8NHrbbrHg@mail.gmail.com

Reported-by: Caspar Duregger <herr.kaste@gmail.com>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Phillip Wood 2020-11-04 15:29:37 +00:00 committed by Junio C Hamano
parent b927c80531
commit e100bea481
2 changed files with 16 additions and 5 deletions
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10
builtin/rebase.c
View File

@ -270,15 +270,15 @@ static int edit_todo_file(unsigned flags)
}
static int get_revision_ranges(struct commit *upstream, struct commit *onto,
struct object_id *orig_head, const char **head_hash,
struct object_id *orig_head, char *head_hash,
char **revisions, char **shortrevisions)
{
struct commit *base_rev = upstream ? upstream : onto;
const char *shorthead;
*head_hash = find_unique_abbrev(orig_head, GIT_MAX_HEXSZ);
find_unique_abbrev_r(head_hash, orig_head, GIT_MAX_HEXSZ);
*revisions = xstrfmt("%s...%s", oid_to_hex(&base_rev->object.oid),
*head_hash);
head_hash);
shorthead = find_unique_abbrev(orig_head, DEFAULT_ABBREV);
@ -327,7 +327,7 @@ static void split_exec_commands(const char *cmd, struct string_list *commands)
static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
{
int ret;
const char *head_hash = NULL;
char head_hash[GIT_MAX_HEXSZ];
char *revisions = NULL, *shortrevisions = NULL;
struct strvec make_script_args = STRVEC_INIT;
struct todo_list todo_list = TODO_LIST_INIT;
@ -335,7 +335,7 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
struct string_list commands = STRING_LIST_INIT_DUP;
if (get_revision_ranges(opts->upstream, opts->onto, &opts->orig_head,
&head_hash, &revisions, &shortrevisions))
head_hash, &revisions, &shortrevisions))
return -1;
if (init_basic_state(&replay,

11
t/t3404-rebase-interactive.sh
View File

@ -1797,6 +1797,17 @@ test_expect_success 'todo has correct onto hash' '
test_i18ngrep "^# Rebase ..* onto $onto" actual
'
test_expect_success 'ORIG_HEAD is updated correctly' '
test_when_finished "git checkout master && git branch -D test-orig-head" &&
git checkout -b test-orig-head A &&
git commit --allow-empty -m A1 &&
git commit --allow-empty -m A2 &&
git commit --allow-empty -m A3 &&
git commit --allow-empty -m A4 &&
git rebase master &&
test_cmp_rev ORIG_HEAD test-orig-head@{1}
'
# This must be the last test in this file
test_expect_success '$EDITOR and friends are unchanged' '
test_editor_unchanged