Subject: [PATCH 2/2] whatchanged: require --i-still-use-this

From: Junio C Hamano <[email-masked]>
Date: Thu, 1 May 2025 14:34:52 -0700

The documentation of "git whatchanged" is pretty explicit that this
has retained for historical reasons to help those whose fingers
cannot be retrained.  Let's see if they still are finding it hard to
type "git log --raw" instead of "git whatchanged" by marking the
command as "nominated for removal", and require "--i-still-use-this"
on the command line.

While at it, update the documentation page to use the new [synopsis]
facility to mark-up the SYNOPSIS part.

Signed-off-by: Junio C Hamano <[email-masked]>
---
 Documentation/git-whatchanged.adoc | 10 ++++++++--
 builtin/log.c                      | 13 +++++++++++++
 t/t4013-diff-various.sh            | 17 +++++++++++++++--
 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/Documentation/git-whatchanged.adoc b/Documentation/git-whatchanged.adoc
index 8e55e0bb1e..d21484026f 100644
--- a/Documentation/git-whatchanged.adoc
+++ b/Documentation/git-whatchanged.adoc
@@ -8,8 +8,14 @@ git-whatchanged - Show logs with differences each commit introduces
 
 SYNOPSIS
 --------
-[verse]
-'git whatchanged' <option>...
+[synopsis]
+git whatchanged <option>...
+
+WARNING
+-------
+`git whatchanged` has been deprecated and is scheduled for removal in
+a future version of Git, as it is merely `git log` with different
+default; `whatchanged` is not even shorter to type than `log --raw`.
 
 DESCRIPTION
 -----------
diff --git a/builtin/log.c b/builtin/log.c
index 04a6ef97bc..0f98ac8a34 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -113,6 +113,13 @@ struct log_config {
 	int fmt_patch_name_max;
 	char *fmt_pretty;
 	char *default_date_mode;
+
+	/*
+	 * Note: git_log_config() does not touch this member and that
+	 * is very deliberate.  This member is only to be used to
+	 * resurrect whatchanged that is deprecated.
+	 */
+	int i_still_use_this;
 };
 
 static void log_config_init(struct log_config *cfg)
@@ -267,6 +274,8 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 		OPT__QUIET(&quiet, N_("suppress diff output")),
 		OPT_BOOL(0, "source", &source, N_("show source")),
 		OPT_BOOL(0, "use-mailmap", &mailmap, N_("use mail map file")),
+		OPT_HIDDEN_BOOL(0, "i-still-use-this", &cfg->i_still_use_this,
+				"<use this deprecated command>"),
 		OPT_ALIAS(0, "mailmap", "use-mailmap"),
 		OPT_CALLBACK_F(0, "clear-decorations", NULL, NULL,
 			       N_("clear all previously-defined decoration filters"),
@@ -656,6 +665,10 @@ int cmd_whatchanged(int argc,
 	opt.def = "HEAD";
 	opt.revarg_opt = REVARG_COMMITTISH;
 	cmd_log_init(argc, argv, prefix, &rev, &opt, &cfg);
+
+	if (!cfg.i_still_use_this)
+		you_still_use_that("git whatchanged");
+
 	if (!rev.diffopt.output_format)
 		rev.diffopt.output_format = DIFF_FORMAT_RAW;
 
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 3855d68dbc..8caab2ee38 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -203,11 +203,19 @@ do
 	test_expect_success "git $cmd # magic is ${magic:-(not used)}" '
 		{
 			echo "$ git $cmd"
+
+			case "$cmd" in
+			whatchanged | whatchanged" "*)
+				run="whatchanged --i-still-use-this"
+				run="$run ${cmd#whatchanged}" ;;
+			*)
+				run=$cmd ;;
+			esac &&
 			case "$magic" in
 			"")
-				GIT_PRINT_SHA1_ELLIPSIS=yes git $cmd ;;
+				GIT_PRINT_SHA1_ELLIPSIS=yes git $run ;;
 			noellipses)
-				git $cmd ;;
+				git $run ;;
 			esac |
 			sed -e "s/^\\(-*\\)$V\\(-*\\)\$/\\1g-i-t--v-e-r-s-i-o-n\2/" \
 			    -e "s/^\\(.*mixed; boundary=\"-*\\)$V\\(-*\\)\"\$/\\1g-i-t--v-e-r-s-i-o-n\2\"/"
@@ -454,6 +462,11 @@ diff-tree --stat --compact-summary initial mode
 diff-tree -R --stat --compact-summary initial mode
 EOF
 
+test_expect_success 'whatchanged needs --i-still-use-this' '
+	test_must_fail git whatchanged >message 2>&1 &&
+	test_grep "nominated for removal" message
+'
+
 test_expect_success 'log -m matches pure log' '
 	git log master >result &&
 	process_diffs result >expected &&
-- 
2.49.0-599-g90c2cffacf