[PATCH v2 0/5] git log: configurable default format for merge diffs

From: Sergey Organov <sorganov@gmail.com>
Date: Apr 13, 2021, 11:41 UTC
Message-ID: <20210413114118.25693-1-sorganov@gmail.com>
In-Reply-To: <20210407225608.14611-1-sorganov@gmail.com>

These patches introduce capability to configure the default format of output of diffs for merge commits by means of new log.diffMerges configuration variable. The default format could be requested by the new value "on" for --diff-merges option (--diff-merges=on).

Then -m and --diff-merges=m are also changed to use the default format, in a backward compatible manner, as visible behavior doesn't change unless user customizes log.diffMerges configuration.

In particular,

  git config log.diffMerges first-parent

will change -m option format from "separate" to "first-parent" that will in turn cause, say,

  git show -m <merge_commit>

to output diff to the first parent only, instead of appending typically large and surprising diff to the second parent at the end of the output.

Updates in v2:

  * Renamed --diff-merges=default to --diff-merges=on. Junio didn't
    like the "default" here, and I agree. Dunno why I've even called
    it "default" in the first place.

Updates in v1:

  * Renamed abbreviated value "def" to full "default"

  * Fixed tests to use "test_config" instead of "git config"

  * Meld all "git config" changes into single commit that includes
    code, documentation, and tests, as they are mutually
    interdependent.

Signed-off-by: Sergey Organov <sorganov@gmail.com>

Sergey Organov (5):
  diff-merges: introduce --diff-merges=on
  diff-merges: refactor set_diff_merges()
  diff-merges: adapt -m to enable default diff format
  diff-merges: introduce log.diffMerges config variable
  doc/diff-options: document new --diff-merges features

 Documentation/config/log.txt   |  5 +++
 Documentation/diff-options.txt | 15 ++++++---
 builtin/log.c                  |  2 ++
 diff-merges.c                  | 58 ++++++++++++++++++++++++----------
 diff-merges.h                  |  2 ++
 t/t4013-diff-various.sh        | 31 ++++++++++++++++++
 t/t9902-completion.sh          |  3 ++
 7 files changed, 95 insertions(+), 21 deletions(-)

Interdiff against v1:

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 31e2bacf5252..6d968b9012dc 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -34,7 +34,7 @@ endif::git-diff[]
 endif::git-format-patch[]
 
 ifdef::git-log[]
---diff-merges=(off|none|default|first-parent|1|separate|m|combined|c|dense-combined|cc)::
+--diff-merges=(off|none|on|first-parent|1|separate|m|combined|c|dense-combined|cc)::
 --no-diff-merges::
 	Specify diff format to be used for merge commits. Default is
 	{diff-merges-default} unless `--first-parent` is in use, in which case
@@ -45,7 +45,7 @@ ifdef::git-log[]
 	Disable output of diffs for merge commits. Useful to override
 	implied value.
 +
---diff-merges=default:::
+--diff-merges=on:::
 --diff-merges=m:::
 -m:::
 	This option makes diff output for merge commits to be shown in
diff --git a/diff-merges.c b/diff-merges.c
index 75630fb8e6b8..f3a9daed7e05 100644
--- a/diff-merges.c
+++ b/diff-merges.c
@@ -67,7 +67,7 @@ static diff_merges_setup_func_t func_by_opt(const char *optarg)
 		return set_combined;
 	else if (!strcmp(optarg, "cc") || !strcmp(optarg, "dense-combined"))
 		return set_dense_combined;
-	else if (!strcmp(optarg, "m") || !strcmp(optarg, "default"))
+	else if (!strcmp(optarg, "m") || !strcmp(optarg, "on"))
 		return set_to_default;
 	return NULL;
 }
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 87cab7867135..87def81699bf 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -452,10 +452,10 @@ diff-tree --stat --compact-summary initial mode
 diff-tree -R --stat --compact-summary initial mode
 EOF
 
-test_expect_success 'log --diff-merges=default matches --diff-merges=separate' '
+test_expect_success 'log --diff-merges=on matches --diff-merges=separate' '
 	git log -p --diff-merges=separate master >result &&
 	process_diffs result >expected &&
-	git log -p --diff-merges=default master >result &&
+	git log -p --diff-merges=on master >result &&
 	process_diffs result >actual &&
 	test_cmp expected actual
 '
@@ -469,7 +469,7 @@ test_expect_success 'git config log.diffMerges first-parent' '
 	git log -p --diff-merges=first-parent master >result &&
 	process_diffs result >expected &&
 	test_config log.diffMerges first-parent &&
-	git log -p --diff-merges=default master >result &&
+	git log -p --diff-merges=on master >result &&
 	process_diffs result >actual &&
 	test_cmp expected actual
 '

-- 
2.25.1