Merge branch 'pw/3.0-commentchar-auto-deprecation'

"core.commentChar=auto" that attempts to dynamically pick a
suitable comment character is non-workable, as it is too much
trouble to support for little benefit, and is marked as deprecated.

* pw/3.0-commentchar-auto-deprecation:
  commit: print advice when core.commentString=auto
  config: warn on core.commentString=auto
  breaking-changes: deprecate support for core.commentString=auto

Author: gitster

Documentation/BreakingChanges.adoc

@@ -239,6 +239,11 @@ These features will be removed.
 +
 The command will be removed.
 
+* Support for `core.commentString=auto` has been deprecated and will
+  be removed in Git 3.0.
++
+cf. <[email protected]>
+
 == Superseded features that will not be deprecated
 
 Some features have gained newer replacements that aim to improve the design in

Documentation/config/core.adoc

@@ -531,9 +531,25 @@ core.commentString::
 	commented, and removes them after the editor returns
 	(default '#').
 +
-If set to "auto", `git-commit` would select a character that is not
+ifndef::with-breaking-changes[]
+If set to "auto", `git-commit` will select a character that is not
 the beginning character of any line in existing commit messages.
-+
+Support for this value is deprecated and will be removed in Git 3.0
+due to the following limitations:
++
+--
+* It is incompatible with adding comments in a commit message
+  template. This includes the conflicts comments added to
+  the commit message by `cherry-pick`, `merge`, `rebase` and
+  `revert`.
+* It is incompatible with adding comments to the commit message
+  in the `prepare-commit-msg` hook.
+* It is incompatible with the `fixup` and `squash` commands when
+  rebasing,
+* It is not respected by `git notes`
+--
++
+endif::with-breaking-changes[]
 Note that these two variables are aliases of each other, and in modern
 versions of Git you are free to use a string (e.g., `//` or `⁑⁕⁑`) with
 `commentChar`. Versions of Git prior to v2.45.0 will ignore

builtin/commit.c

@@ -695,6 +695,7 @@ static int author_date_is_interesting(void)
 	return author_message || force_date;
 }
 
+#ifndef WITH_BREAKING_CHANGES
 static void adjust_comment_line_char(const struct strbuf *sb)
 {
 	char candidates[] = "#;@!$%^&|:";
@@ -732,6 +733,7 @@ static void adjust_comment_line_char(const struct strbuf *sb)
 	free(comment_line_str_to_free);
 	comment_line_str = comment_line_str_to_free = xstrfmt("%c", *p);
 }
+#endif /* !WITH_BREAKING_CHANGES */
 
 static void prepare_amend_commit(struct commit *commit, struct strbuf *sb,
 				struct pretty_print_context *ctx)
@@ -928,8 +930,10 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 	if (fwrite(sb.buf, 1, sb.len, s->fp) < sb.len)
 		die_errno(_("could not write commit template"));
 
+#ifndef WITH_BREAKING_CHANGES
 	if (auto_comment_line_char)
 		adjust_comment_line_char(&sb);
+#endif /* !WITH_BREAKING_CHANGES */
 	strbuf_release(&sb);
 
 	/* This checks if committer ident is explicitly given */
@@ -1793,6 +1797,9 @@ int cmd_commit(int argc,
 	show_usage_with_options_if_asked(argc, argv,
 					 builtin_commit_usage, builtin_commit_options);
 
+#ifndef WITH_BREAKING_CHANGES
+	warn_on_auto_comment_char = true;
+#endif /* !WITH_BREAKING_CHANGES */
 	prepare_repo_settings(the_repository);
 	the_repository->settings.command_requires_full_index = 0;
 

builtin/merge.c

@@ -1379,6 +1379,9 @@ int cmd_merge(int argc,
 	show_usage_with_options_if_asked(argc, argv,
 					 builtin_merge_usage, builtin_merge_options);
 
+#ifndef WITH_BREAKING_CHANGES
+	warn_on_auto_comment_char = true;
+#endif /* !WITH_BREAKING_CHANGES */
 	prepare_repo_settings(the_repository);
 	the_repository->settings.command_requires_full_index = 0;
 

builtin/rebase.c

@@ -1242,6 +1242,9 @@ int cmd_rebase(int argc,
 					 builtin_rebase_usage,
 					 builtin_rebase_options);
 
+#ifndef WITH_BREAKING_CHANGES
+	warn_on_auto_comment_char = true;
+#endif /* !WITH_BREAKING_CHANGES */
 	prepare_repo_settings(the_repository);
 	the_repository->settings.command_requires_full_index = 0;
 

builtin/revert.c

@@ -4,6 +4,7 @@
 #include "builtin.h"
 #include "parse-options.h"
 #include "diff.h"
+#include "environment.h"
 #include "gettext.h"
 #include "revision.h"
 #include "rerere.h"
@@ -285,6 +286,9 @@ int cmd_revert(int argc,
 	struct replay_opts opts = REPLAY_OPTS_INIT;
 	int res;
 
+#ifndef WITH_BREAKING_CHANGES
+	warn_on_auto_comment_char = true;
+#endif /* !WITH_BREAKING_CHANGES */
 	opts.action = REPLAY_REVERT;
 	sequencer_init_config(&opts);
 	res = run_sequencer(argc, argv, prefix, &opts);
@@ -302,6 +306,9 @@ struct repository *repo UNUSED)
 	struct replay_opts opts = REPLAY_OPTS_INIT;
 	int res;
 
+#ifndef WITH_BREAKING_CHANGES
+	warn_on_auto_comment_char = true;
+#endif /* !WITH_BREAKING_CHANGES */
 	opts.action = REPLAY_PICK;
 	sequencer_init_config(&opts);
 	res = run_sequencer(argc, argv, prefix, &opts);