line-log: integrate -L with the standard log output pipeline

[mmontalbo]

Since its introduction, git log -L has short-circuited from
log_tree_commit() into its own output function, bypassing
log_tree_diff() and log_tree_diff_flush(). This skips no_free
save/restore, always_show_header, diff_free() cleanup, and
means that pickaxe (-S, -G, --find-object) and --diff-filter
cannot suppress commits whose pairs are all filtered out, because
show_log() runs before diffcore_std().

This series restructures the flow so that -L goes through the
same log_tree_diff() -> log_tree_diff_flush() path as normal
single-parent and merge diffs, then uses that to enable several
non-patch diff formats.

Patch 1: revision: move -L setup before output_format-to-diff derivation

Preparatory reorder in setup_revisions(). The -L block sets a
default DIFF_FORMAT_PATCH when no format is requested; move it
before the derivation of revs->diff from output_format so the
default is visible to that check. No behavior change on its own.

Patch 2: line-log: integrate -L output with the standard log-tree pipeline

Rename line_log_print() to line_log_queue_pairs(), stripping it
down to only queue pre-computed filepairs. log_tree_diff_flush()
handles show_log(), diffcore_std(), and diff_flush(). This
fixes pickaxe and --diff-filter suppression, and aligns the
commit/diff separator with the rest of log output. Also rejects
--full-diff, which is meaningless when filepairs are pre-computed.

Patch 3: line-log: allow non-patch diff formats with -L

Expand the allowlist to accept --raw, --name-only,
--name-status, and --summary. These only read filepair metadata
already set by the line-log machinery. Diff stat formats (--stat,
--numstat, --shortstat, --dirstat) remain blocked because they
call compute_diffstat() on full blob content and would show
whole-file statistics rather than range-scoped ones.

cc: "D. Ben Knoble" ben.knoble@gmail.com

[mmontalbo]

/preview

[gitgitgadget]

Preview email sent as pull.2094.git.1777348749.gitgitgadget@gmail.com

[mmontalbo]

/submit

[gitgitgadget]

Submitted as pull.2094.git.1777349126.gitgitgadget@gmail.com

To fetch this version into FETCH_HEAD:

git fetch https://github.com/gitgitgadget/git/ pr-2094/mmontalbo/mm/line-log-use-log-tree-diff-flush-v1

To fetch this version to local tag pr-2094/mmontalbo/mm/line-log-use-log-tree-diff-flush-v1:

git fetch --no-tags https://github.com/gitgitgadget/git/ tag pr-2094/mmontalbo/mm/line-log-use-log-tree-diff-flush-v1

[gitgitgadget]

This branch is now known as mm/line-log-cleanup.

[gitgitgadget]

This patch series was integrated into seen via git@7dd37ea.

[gitgitgadget]

There was a status update in the "New Topics" section about the branch mm/line-log-cleanup on the Git mailing list:

Code clean-up.

Comments?
source: <pull.2094.git.1777349126.gitgitgadget@gmail.com>

[gitgitgadget]

This patch series was integrated into seen via git@46c1ebf.

[gitgitgadget]

This patch series was integrated into seen via git@a143674.

[gitgitgadget]

This patch series was integrated into seen via git@f406f5f.

[gitgitgadget]

This patch series was integrated into seen via git@ec1873e.

[gitgitgadget]

There was a status update in the "Cooking" section about the branch mm/line-log-cleanup on the Git mailing list:

Code clean-up.

Comments?
source: <pull.2094.git.1777349126.gitgitgadget@gmail.com>

[gitgitgadget]

This patch series was integrated into seen via git@eb9f7d5.

[gitgitgadget]

This patch series was integrated into seen via git@9781aa1.

[gitgitgadget]

Junio C Hamano wrote on the Git mailing list (how to reply to this email):

"Michael Montalbo via GitGitGadget" <gitgitgadget@gmail.com> writes:

> Since its introduction, git log -L has short-circuited from
> log_tree_commit() into its own output function, bypassing log_tree_diff()
> and log_tree_diff_flush(). This skips no_free save/restore,
> always_show_header, diff_free() cleanup, and means that pickaxe (-S, -G,
> --find-object) and --diff-filter cannot suppress commits whose pairs are all
> filtered out, because show_log() runs before diffcore_std().
>
> This series restructures the flow so that -L goes through the same
> log_tree_diff() -> log_tree_diff_flush() path as normal single-parent and
> merge diffs, then uses that to enable several non-patch diff formats.

This unfortunately saw no reviews and

  https://lore.kernel.org/git/pull.2094.git.1777349126.gitgitgadget@gmail.com/

does not show the previous rouns so I am assuming nobody is
interested in the topic?  

Or are people more busily writing their own patches than reviewing
others' patches?  Unfortunately that is not sustainable.




> Patch 1: revision: move -L setup before output_format-to-diff derivation
>
> Preparatory reorder in setup_revisions(). The -L block sets a default
> DIFF_FORMAT_PATCH when no format is requested; move it before the derivation
> of revs->diff from output_format so the default is visible to that check. No
> behavior change on its own.
>
> Patch 2: line-log: integrate -L output with the standard log-tree pipeline
>
> Rename line_log_print() to line_log_queue_pairs(), stripping it down to only
> queue pre-computed filepairs. log_tree_diff_flush() handles show_log(),
> diffcore_std(), and diff_flush(). This fixes pickaxe and --diff-filter
> suppression, and aligns the commit/diff separator with the rest of log
> output. Also rejects --full-diff, which is meaningless when filepairs are
> pre-computed.
>
> Patch 3: line-log: allow non-patch diff formats with -L
>
> Expand the allowlist to accept --raw, --name-only, --name-status, and
> --summary. These only read filepair metadata already set by the line-log
> machinery. Diff stat formats (--stat, --numstat, --shortstat, --dirstat)
> remain blocked because they call compute_diffstat() on full blob content and
> would show whole-file statistics rather than range-scoped ones.
>
> Michael Montalbo (3):
>   revision: move -L setup before output_format-to-diff derivation
>   line-log: integrate -L output with the standard log-tree pipeline
>   line-log: allow non-patch diff formats with -L
>
>  Documentation/line-range-options.adoc         | 10 +-
>  line-log.c                                    | 30 ++----
>  line-log.h                                    |  2 +-
>  log-tree.c                                    |  9 +-
>  revision.c                                    | 25 +++--
>  t/t4211-line-log.sh                           | 99 ++++++++++++++++---
>  t/t4211/sha1/expect.parallel-change-f-to-main |  1 -
>  .../sha256/expect.parallel-change-f-to-main   |  1 -
>  8 files changed, 120 insertions(+), 57 deletions(-)
>
>
> base-commit: 9f223ef1c026d91c7ac68cc0211bde255dda6199
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2094%2Fmmontalbo%2Fmm%2Fline-log-use-log-tree-diff-flush-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2094/mmontalbo/mm/line-log-use-log-tree-diff-flush-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/2094

[gitgitgadget]

This patch series was integrated into seen via git@67cdb16.

[gitgitgadget]

There was a status update in the "Cooking" section about the branch mm/line-log-cleanup on the Git mailing list:

Code clean-up.

Comments?
cf. <xmqqfr3xp98b.fsf@gitster.g>
source: <pull.2094.git.1777349126.gitgitgadget@gmail.com>

[gitgitgadget]

This patch series was integrated into seen via git@df46f9d.

[gitgitgadget]

This patch series was integrated into seen via git@3cd0553.

[gitgitgadget]

This patch series was integrated into seen via git@15f8769.

[gitgitgadget]

This patch series was integrated into seen via git@36f0732.

[gitgitgadget]

There was a status update in the "Cooking" section about the branch mm/line-log-cleanup on the Git mailing list:

Code clean-up.

Comments?
cf. <xmqqfr3xp98b.fsf@gitster.g>
source: <pull.2094.git.1777349126.gitgitgadget@gmail.com>

[gitgitgadget]

This patch series was integrated into seen via git@5ac231a.

[gitgitgadget]

This patch series was integrated into seen via git@3c5be57.

[gitgitgadget]

This patch series was integrated into seen via git@0f29831.

[gitgitgadget]

There was a status update in the "Cooking" section about the branch mm/line-log-cleanup on the Git mailing list:

Code clean-up.

Comments?
cf. <xmqqfr3xp98b.fsf@gitster.g>
source: <pull.2094.git.1777349126.gitgitgadget@gmail.com>

[gitgitgadget]

This patch series was integrated into seen via git@cbe78b1.

[gitgitgadget]

This patch series was integrated into seen via git@68e5ad2.

[gitgitgadget]

This patch series was integrated into seen via git@a7f542a.

[gitgitgadget]

This patch series was integrated into seen via git@cbd5b5c.

[gitgitgadget]

"D. Ben Knoble" wrote on the Git mailing list (how to reply to this email):

Hi Michael,

On Tue, Apr 28, 2026 at 12:06 AM Michael Montalbo via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> Since its introduction, git log -L has short-circuited from
> log_tree_commit() into its own output function, bypassing log_tree_diff()
> and log_tree_diff_flush(). This skips no_free save/restore,
> always_show_header, diff_free() cleanup, and means that pickaxe (-S, -G,
> --find-object) and --diff-filter cannot suppress commits whose pairs are all
> filtered out, because show_log() runs before diffcore_std().
>
> This series restructures the flow so that -L goes through the same
> log_tree_diff() -> log_tree_diff_flush() path as normal single-parent and
> merge diffs, then uses that to enable several non-patch diff formats.

Cleanup by itself to shrink the number of concepts in the code is
already a good thing IMO, so getting additional features out of it is
even nicer.

> Patch 1: revision: move -L setup before output_format-to-diff derivation
>
> Preparatory reorder in setup_revisions(). The -L block sets a default
> DIFF_FORMAT_PATCH when no format is requested; move it before the derivation
> of revs->diff from output_format so the default is visible to that check. No
> behavior change on its own.

Straightforward, nice.

>
> Patch 2: line-log: integrate -L output with the standard log-tree pipeline
>
> Rename line_log_print() to line_log_queue_pairs(), stripping it down to only
> queue pre-computed filepairs. log_tree_diff_flush() handles show_log(),
> diffcore_std(), and diff_flush(). This fixes pickaxe and --diff-filter
> suppression, and aligns the commit/diff separator with the rest of log
> output. Also rejects --full-diff, which is meaningless when filepairs are
> pre-computed.

At first I questioned the removal of the DIFF_FORMAT_NO_OUTPUT
conditional in line_log_queue_pairs, but now that it only queues pairs
it shouldn't be checking output formats. Good.

I also noted that log_tree_diff() returns the result of
log_tree_diff_flush() in the -L case, which is a bit different from
the other patterns. I think the difference is that the other cases
have some conditional logic around the log_tree_diff_flush cases (?)
but I'm not sure. Perhaps that branch should also be looking at
opt->loginfo ?

Finally, I wonder if in describing the removal of the early return:

> - Remove the early return in log_tree_commit() that bypassed
>   no_free save/restore, always_show_header, and diff_free().

we might want to be more explicit that this is _because_ line-level
diff is now handled in the regular pipeline?

[I suppose we could, in theory, split the rejection of --full-diff to
a separate prep commit, idk.j]

> Patch 3: line-log: allow non-patch diff formats with -L
>
> Expand the allowlist to accept --raw, --name-only, --name-status, and
> --summary. These only read filepair metadata already set by the line-log
> machinery. Diff stat formats (--stat, --numstat, --shortstat, --dirstat)
> remain blocked because they call compute_diffstat() on full blob content and
> would show whole-file statistics rather than range-scoped ones.

Short and sweet.

The stat formats are kind of like --full-diff, and I think they should
probably all be rejected or all allowed: since the stats are based on
the full-diff, it makes sense to enable them if we can also make -L +
--full-diff semantically sensible.

Otherwise, we'd need to find a way to make the stat formats scoped for -L.

> Michael Montalbo (3):
>   revision: move -L setup before output_format-to-diff derivation
>   line-log: integrate -L output with the standard log-tree pipeline
>   line-log: allow non-patch diff formats with -L
>
>  Documentation/line-range-options.adoc         | 10 +-
>  line-log.c                                    | 30 ++----
>  line-log.h                                    |  2 +-
>  log-tree.c                                    |  9 +-
>  revision.c                                    | 25 +++--
>  t/t4211-line-log.sh                           | 99 ++++++++++++++++---
>  t/t4211/sha1/expect.parallel-change-f-to-main |  1 -
>  .../sha256/expect.parallel-change-f-to-main   |  1 -
>  8 files changed, 120 insertions(+), 57 deletions(-)
>
>
> base-commit: 9f223ef1c026d91c7ac68cc0211bde255dda6199
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2094%2Fmmontalbo%2Fmm%2Fline-log-use-log-tree-diff-flush-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2094/mmontalbo/mm/line-log-use-log-tree-diff-flush-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/2094
> --
> gitgitgadget

A few other comments:

- Tests should use test_grep; some do, but some don't.
- There is one occurrence of "sed | grep" that I wonder if we want to
rewrite to avoid issues with exit status one side of the pipe?

Thanks for working on this!

[Apologies for the unusual review format; this was easier for me at
the moment than digging up the individual patches, and I don't think
_most_ of the review would benefit from spreading out across multiple
mails.]

-- 
D. Ben Knoble

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