Re: [PATCH v4 0/2] reflog: add format %gb

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Harald

On 04/11/2026 21:15, Harald Nordgren via GitGitGadget wrote:
> 
> It follows branch switches, branch renames and rebases, including "git
> rebase ", rebases of a detached HEAD and rebases of a branch that was
> already up to date. When HEAD was detached, the entry shows "detached at ".

The "detached at " labels show the commit before we switch away from a
detached HEAD, not the commit where HEAD was detached. The parsing of
"rebase: checkout <revision>" is still not quite right - it treats
"origin/main" as a branch name and is confused by commits where the
subject starts with "checkout " (I think the way to avoid that is to
check that the reflog message does not match the commit subject [1]).
Here is a failing test for those issues which also checks we handle
':' in a url in $GIT_REFLOG_ACTION correctly.

test_expect_success '%gb labels branches and detached HEADs' '
	test_create_repo origin &&
	(
		cd origin &&
		test_commit O1 &&
		test_commit O2
	) &&
	git clone origin downstream &&
	(
		cd origin &&
		test_commit O3
	) &&
	(
		cd downstream &&
		test_commit L1 &&
		git branch side &&
		test_commit L2 &&
		git pull -r "file://$TRASH_DIRECTORY/origin" &&
		test_commit L3 &&
		GIT_REFLOG_ACTION="sync switch" git rebase -i FETCH_HEAD side^0 &&
		H1=$(git rev-parse --short HEAD) &&
		test_commit "checkout main" L4.t L4 L4 &&
		git rebase FETCH_HEAD side &&
		test_commit L5 &&
		git rebase origin/main origin/main &&
		H2=$(git rev-parse --short HEAD) &&
		test_commit L6 &&
		git rebase main refs/heads/main &&
		H3=$(git rev-parse --short HEAD) &&
		test_commit L7 &&
		git switch side &&
		test_commit L8 &&
		git checkout origin/main &&
		H4=$(git rev-parse --short HEAD) &&
		test_commit L9 &&

		cat >expect <<-EOF &&
		commit: l9 (detached at $H4) &&
		checkout: moving from side to origin/main (detached at $H4)
		commit: L8 (side)
		checkout: moving from $(git rev-parse L7) to side (side)
		commit: L7 (detached at $H3)
		rebase: checkout refs/heads/main (detached at $H3)
		commit: L6 (detached at $H2)
		rebase: checkout origin/main (detached at $H2)
		commit: L5 (side)
		rebase (finish): returning to refs/heads/side (side)
		rebase (pick): L1 (side)
		rebase (start): checkout FETCH_HEAD (side)
		commit: checkout main (detached at $H1)
		sync switch (pick): L1 (detached at $H1)
		sync switch (start): checkout FETCH_HEAD (detached at $H1)
		commit: L3 (main)
		pull -r file://$TRASH_DIRECTORY/origin (finish): returning to refs/heads/main (main)
		pull -r file://$TRASH_DIRECTORY/origin (pick): L2 (main)
		pull -r file://$TRASH_DIRECTORY/origin (pick): L1 (main)
		pull -r file://$TRASH_DIRECTORY/origin (start): checkout $(git rev-parse FETCH_HEAD) (main)
		commit: L2 (main)
		commit: L1 (main)
		clone: from $TRASH_DIRECTORY/origin (main)
		EOF

		git log -g --format="%gs (%gb)" >actual &&
		test_cmp expect actual
	)
'

Thanks

Phillip

[1] https://github.com/phillipwood/git/blob/c11b0dcb38d4dbe26c41053569d4fae27fdf0de6/object-name.c#L1301

> 
> Changes in v4:
> 
>   * %gb now names the right branch when git rebase <upstream> <branch> runs
>     with GIT_REFLOG_ACTION set.
>   * Reworded the %gb commit message.
> 
> Changes in v3:
> 
>   * Dropped --operations.
>   * Replaced --historical-branch with a %gb placeholder for --format, e.g.
>     git log -g --format='%h %gd: (%gb) %gs'.
>   * %gb names the right branch after git rebase <upstream> <branch>, a rebase
>     of a detached HEAD and an up-to-date rebase.
>   * Named the returning to and checkout reflog strings in reflog.h too.
> 
> Changes in v2:
> 
>   * Move the "historical branch" rightward in the display for cleaner
>     alignment.
>   * Improve commit messages.
> 
> Harald Nordgren (2):
>    reflog: name the strings that mark switches, renames and rebase steps
>    pretty: add %gb to name the branch of each reflog entry
> 
>   Documentation/pretty-formats.adoc |   3 +
>   builtin/branch.c                  |   3 +-
>   builtin/checkout.c                |   3 +-
>   builtin/rebase.c                  |  19 ++--
>   object-name.c                     |   3 +-
>   pretty.c                          |   4 +
>   reflog-walk.c                     | 167 ++++++++++++++++++++++++++++--
>   reflog-walk.h                     |   2 +
>   reflog.h                          |   8 ++
>   sequencer.c                       |  13 +--
>   t/t1414-reflog-walk.sh            | 137 ++++++++++++++++++++++++
>   wt-status.c                       |   3 +-
>   12 files changed, 340 insertions(+), 25 deletions(-)
> 
> 
> base-commit: 750f5de7dfe9a4062f95088212b063f189d50e91
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2448%2FHaraldNordgren%2Freflog-operations-v4
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2448/HaraldNordgren/reflog-operations-v4
> Pull-Request: https://github.com/git/git/pull/2448
> 
> Range-diff vs v3:
> 
>   1:  4d779e8da3 = 1:  f960a24b8b reflog: name the strings that mark switches, renames and rebase steps
>   2:  dee548f9b1 ! 2:  99a1047702 pretty: add %gb to name the branch of each reflog entry
>       @@ Commit message
>                1a2b3c4 HEAD@{3}: (main) commit: fix typo
>                5d6e7f8 HEAD@{4}: (main) checkout: moving from topic to main
>        
>       -    The branch is read from the entries that branch switches, branch
>       -    renames and rebases leave behind. The entries of a rebase are named
>       -    after the branch being rebased. When HEAD was detached, the entry
>       -    shows "detached at <commit>" with the commit HEAD was at when it
>       -    moved on. When nothing older in the reflog says which branch a rebase
>       -    started on, the rebase is taken to have started on the branch it
>       -    rebased. For the reflog of any other ref, "%gb" is the name of that
>       -    ref.
>       +    The branch is read from the entries created by branch switches,
>       +    branch renames and rebases. The entries of a rebase are labeled with
>       +    the branch being rebased. When HEAD was detached, the entry shows
>       +    "detached at <commit>" with the commit HEAD was at when it moved on.
>       +    When nothing older in the reflog says which branch a rebase started
>       +    on, the rebase is taken to have started on the branch it rebased. For
>       +    the reflog of any other ref, "%gb" is the name of that ref.
>        
>            Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
>        
>       @@ reflog-walk.c: static void complete_reflogs_clear(void *util, const char *str UN
>        +	return p;
>        +}
>        +
>       ++static const char *skip_rebase_checkout(const char *message)
>       ++{
>       ++	const char *p = strstr(message, " (");
>       ++	const char *colon = strstr(message, ": ");
>       ++
>       ++	if (!colon || (p && p < colon) ||
>       ++	    !skip_prefix(colon + 2, REFLOG_CHECKOUT, &p))
>       ++		return NULL;
>       ++	return p;
>       ++}
>       ++
>        +struct branch_move {
>        +	const char *from, *to;
>        +	size_t from_len, to_len;
>       @@ reflog-walk.c: static void complete_reflogs_clear(void *util, const char *str UN
>        +		   skip_prefix(to, REFLOG_RETURNING_TO, &to)) {
>        +		move->from = move->to = to;
>        +		move->from_len = strcspn(to, "\n");
>       -+	} else if (skip_prefix(message, "rebase: " REFLOG_CHECKOUT, &to)) {
>       ++	} else if ((to = skip_rebase_checkout(message))) {
>        +		move->to = to;
>        +	} else if (!skip_rebase_step(message, REFLOG_STEP_START)) {
>        +		return false;
>       @@ t/t1414-reflog-walk.sh: test_expect_success 'walk prefers reflog to ref tip' '
>        +	)
>        +'
>        +
>       ++test_expect_success '%gb follows "git rebase <upstream> <branch>" with GIT_REFLOG_ACTION' '
>       ++	(
>       ++		cd branches &&
>       ++		git switch main &&
>       ++		GIT_REFLOG_ACTION="sync switch" git rebase main topic &&
>       ++
>       ++		cat >expect <<-\EOF &&
>       ++		(topic) sync switch: checkout topic
>       ++		(main) checkout: moving from topic to main
>       ++		EOF
>       ++		git log -g -2 --format="(%gb) %gs" >actual &&
>       ++		test_cmp expect actual
>       ++	)
>       ++'
>       ++
>        +test_expect_success '%gb names a detached HEAD by the commit it was left at' '
>        +	(
>        +		cd branches &&
>