[PATCH v2 0/4] line-log: route -L output through the standard diff pipeline

["Michael Montalbo via GitGitGadget" <gitgitgadget@gmail.com>]

git log -L has bypassed the standard diff pipeline since its introduction,
using dump_diff_hacky() to hand-roll diff output. A NEEDSWORK comment has
acknowledged this from the start. This series removes dump_diff_hacky() and
routes -L output through builtin_diff() / fn_out_consume(), so that diff
formatting options like --word-diff, --color-moved, -w, and pickaxe options
(-S, -G) work with -L.

This replaces my earlier series "line-log: fix -L with pickaxe options" [1].
Patch 1 is the crash fix from that series (unchanged). Patch 2/2 from that
series (rejecting -S/-G) is dropped because this series makes those options
work instead of rejecting them.

[1]
https://lore.kernel.org/git/pull.2061.git.1772651484.gitgitgadget@gmail.com/

Patch 1 fixes a crash when combining -L with pickaxe options and a rename.

Patch 2 is the core change: callback wrappers filter xdiff's output to
tracked line ranges, and line ranges are carried on diff_filepair so each
file's ranges travel with its filepair through the pipeline. diffcore_std()
runs at output time, so pickaxe, --orderfile, and --diff-filter also work.

Patch 3 adds tests covering the newly-working options.

Patch 4 updates documentation.

User-visible output change: -L output now includes index lines, new file
mode headers, and funcname context in @@ headers that were previously
missing. Tools parsing -L output may need to handle these additional lines.

Known limitations not addressed in this series:

 * line_log_print() still calls show_log() and diff_flush() directly,
   bypassing log_tree_diff_flush(). The early return in log_tree_commit()
   (and its associated NEEDSWORK about no_free not being restored) is
   pre-existing. Restructuring -L to flow through log_tree_diff_flush() is a
   larger change that would affect separator and header logic; it is left
   for a follow-up.

 * Non-patch diff formats (--raw, --numstat, --stat, etc.) remain
   unimplemented for -L.

cc: "Kristoffer Haugsbakk" kristofferhaugsbakk@fastmail.com

Changes since v1:

 * Patch 4/4: fix documentation formatting: use line continuation
   instead of indentation (Kristoffer Haugsbakk)

Michael Montalbo (4):
  line-log: fix crash when combined with pickaxe options
  line-log: route -L output through the standard diff pipeline
  t4211: add tests for -L with standard diff options
  doc: note that -L supports patch formatting and pickaxe options

 Documentation/line-range-options.adoc         |   4 +
 diff.c                                        | 279 +++++++++++++-
 diffcore.h                                    |  16 +
 line-log.c                                    | 196 ++--------
 line-log.h                                    |  14 +-
 revision.c                                    |   2 +
 t/t4211-line-log.sh                           | 348 +++++++++++++++++-
 t/t4211/sha1/expect.beginning-of-file         |   4 +
 t/t4211/sha1/expect.end-of-file               |  11 +-
 t/t4211/sha1/expect.move-support-f            |   5 +
 t/t4211/sha1/expect.multiple                  |  10 +-
 t/t4211/sha1/expect.multiple-overlapping      |   7 +
 t/t4211/sha1/expect.multiple-superset         |   7 +
 t/t4211/sha1/expect.no-assertion-error        |  12 +-
 t/t4211/sha1/expect.parallel-change-f-to-main |   7 +
 t/t4211/sha1/expect.simple-f                  |   4 +
 t/t4211/sha1/expect.simple-f-to-main          |   5 +
 t/t4211/sha1/expect.simple-main               |  11 +-
 t/t4211/sha1/expect.simple-main-to-end        |  11 +-
 t/t4211/sha1/expect.two-ranges                |  10 +-
 t/t4211/sha1/expect.vanishes-early            |  10 +-
 t/t4211/sha256/expect.beginning-of-file       |   4 +
 t/t4211/sha256/expect.end-of-file             |  11 +-
 t/t4211/sha256/expect.move-support-f          |   5 +
 t/t4211/sha256/expect.multiple                |  10 +-
 t/t4211/sha256/expect.multiple-overlapping    |   7 +
 t/t4211/sha256/expect.multiple-superset       |   7 +
 t/t4211/sha256/expect.no-assertion-error      |  12 +-
 .../sha256/expect.parallel-change-f-to-main   |   7 +
 t/t4211/sha256/expect.simple-f                |   4 +
 t/t4211/sha256/expect.simple-f-to-main        |   5 +
 t/t4211/sha256/expect.simple-main             |  11 +-
 t/t4211/sha256/expect.simple-main-to-end      |  11 +-
 t/t4211/sha256/expect.two-ranges              |  10 +-
 t/t4211/sha256/expect.vanishes-early          |  10 +-
 35 files changed, 870 insertions(+), 217 deletions(-)


base-commit: 7b2bccb0d58d4f24705bf985de1f4612e4cf06e5
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2065%2Fmmontalbo%2Fspike-xdiff-line-range-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2065/mmontalbo/spike-xdiff-line-range-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/2065

Range-diff vs v1:

 1:  e7b8cc2c78 ! 1:  ccfc1b03ff line-log: fix crash when combined with pickaxe options
     @@ t/t4211-line-log.sh: test_expect_success 'show line-log with graph' '
      +		--find-object=$(git rev-parse HEAD:file) >actual
      +'
      +
     ++# Commit-level filtering with pickaxe does not yet work for -L.
     ++# show_log() prints the commit header before diffcore_std() runs
     ++# pickaxe, so commits cannot be suppressed even when no diff pairs
     ++# survive filtering.  Fixing this would require deferring show_log()
     ++# until after diffcore_std(), which is a larger restructuring of the
     ++# log-tree output pipeline.
      +test_expect_failure '-L -G should filter commits by pattern' '
      +	git log --format="%s" --no-patch -L 1,1:file -G "nomatch" >actual &&
      +	test_must_be_empty actual
 2:  6921b07a0f = 2:  4e2bc55082 line-log: route -L output through the standard diff pipeline
 3:  09e00d3f82 = 3:  cf7720ae98 t4211: add tests for -L with standard diff options
 4:  0d3e84a088 ! 4:  93e771b7cd doc: note that -L supports patch formatting and pickaxe options
     @@ Commit message
      
       ## Documentation/line-range-options.adoc ##
      @@
     - 	Patch output can be suppressed using `--no-patch`, but other diff formats
       	(namely `--raw`, `--numstat`, `--shortstat`, `--dirstat`, `--summary`,
       	`--name-only`, `--name-status`, `--check`) are not currently implemented.
     -++
     -+	Patch formatting options such as `--word-diff`, `--color-moved`,
     -+	`--no-prefix`, and whitespace options (`-w`, `-b`) are supported,
     -+	as are pickaxe options (`-S`, `-G`).
       +
     ++Patch formatting options such as `--word-diff`, `--color-moved`,
     ++`--no-prefix`, and whitespace options (`-w`, `-b`) are supported,
     ++as are pickaxe options (`-S`, `-G`).
     +++
       include::line-range-format.adoc[]

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