patch, 2 partsdocument deprecation of log.mailmap=false default

diff --git a/builtin/log.c b/builtin/log.c
index 7c8767d3bc..5ee150be04 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -47,7 +47,7 @@ static int default_follow;
 static int default_show_signature;
 static int decoration_style;
 static int decoration_given;
-static int use_mailmap_config;
+static int use_mailmap_config = -1;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static const char *fmt_pretty;
 
@@ -151,6 +151,16 @@ static void cmd_log_init_defaults(struct rev_info *rev)
 		parse_date_format(default_date_mode, &rev->date_mode);
 }
 
+static char warn_unspecified_mailmap_msg[] =
+N_("log.mailmap is not set; its implicit value will change in an\n"
+   "upcoming release. To squelch this message and preserve current\n"
+   "behaviour, set the log.mailmap configuration value to false.\n"
+   "\n"
+   "To squelch this message and adopt the new behaviour now, set the\n"
+   "log.mailmap configuration value to true.\n"
+   "\n"
+   "See 'git help config' and search for 'log.mailmap' for further information.");
+
 static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 			 struct rev_info *rev, struct setup_revision_opt *opt)
 {
@@ -188,6 +198,11 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 			     PARSE_OPT_KEEP_ARGV0 | PARSE_OPT_KEEP_UNKNOWN |
 			     PARSE_OPT_KEEP_DASHDASH);
 
+	if (mailmap < 0) {
+		warning("%s\n", _(warn_unspecified_mailmap_msg));
+		mailmap = 0;
+	}
+
 	if (quiet)
 		rev->diffopt.output_format |= DIFF_FORMAT_NO_OUTPUT;
 	argc = setup_revisions(argc, argv, rev, opt);

Documentation/config/log.txt, Documentation/git-log.txt

diff --git a/Documentation/config/log.txt b/Documentation/config/log.txt
index 78d9e4453a..7798e10cb0 100644
--- a/Documentation/config/log.txt
+++ b/Documentation/config/log.txt
@@ -40,4 +40,5 @@ log.showSignature::
 
 log.mailmap::
 	If true, makes linkgit:git-log[1], linkgit:git-show[1], and
-	linkgit:git-whatchanged[1] assume `--use-mailmap`.
+	linkgit:git-whatchanged[1] assume `--use-mailmap`, otherwise
+	assume `--no-use-mailmap`. False by default.
diff --git a/Documentation/git-log.txt b/Documentation/git-log.txt
index b02e922dc3..b406bc4c48 100644
--- a/Documentation/git-log.txt
+++ b/Documentation/git-log.txt
@@ -49,7 +49,7 @@ OPTIONS
 	Print out the ref name given on the command line by which each
 	commit was reached.
 
---use-mailmap::
+--[no-]use-mailmap::
 	Use mailmap file to map author and committer names and email
 	addresses to canonical real names and email addresses. See
 	linkgit:git-shortlog[1].

t/t0203-gettext-setlocale-sanity.sh, t/t9700-perl-git.sh

diff --git a/t/t0203-gettext-setlocale-sanity.sh b/t/t0203-gettext-setlocale-sanity.sh
index 0ce1f22eff..76f774c8b8 100755
--- a/t/t0203-gettext-setlocale-sanity.sh
+++ b/t/t0203-gettext-setlocale-sanity.sh
@@ -10,7 +10,7 @@ test_description="The Git C functions aren't broken by setlocale(3)"
 test_expect_success 'git show a ISO-8859-1 commit under C locale' '
 	. "$TEST_DIRECTORY"/t3901/8859-1.txt &&
 	test_commit "iso-c-commit" iso-under-c &&
-	git show >out 2>err &&
+	git show --use-mailmap >out 2>err &&
 	test_must_be_empty err &&
 	grep -q "iso-c-commit" out
 '


4212.3 is the same way.

4212.4 raises an interesting question.  It wants to see the output
of this command:

	git log --format="%an+%ae+%ad" broken_email >actual.out 2>actual.err &&

The question is, when the user explicitly asked for the "true"
identity values (not the mapped one via %aN, %aE and their friends),
if --use-mailmap should affect the outcome?

A secondary question is if we should be issuing a warning against
this command line in the first place, if the answer to the above
question is "no" (i.e. --[no-]use-mailmap, and the future default
switch, do not affect the outcome).  There is no point issuing a
warning if the command line is already future-proofed.

7006.43 (among others) expects its "colorful" shell helper function
to be a reliable way to detect if color escape sequence is in use in
the output but the helper only reads the first line and expects it
to always begin with the colored "commit 0c9f6db7183a...", which fails
when an error or a warning message comes first.  I think the best fix
there should be to make the helper more robust, perhaps by borrowing
ideas from test-lib-functions.sh::test_decode_color, i.e. find byte
sequence "\033[m" in there (I think assuming the presence of RESET
sequence alone is sufficient for the purpose of t7006 tests that
wants to see "have we tried to color or emit non-colored output?".

A possible workaround for 9007 would be to set log.mailmap=true in
the set-up step, but there may be a better alternative.

diff --git a/t/t9700-perl-git.sh b/t/t9700-perl-git.sh
index 102c133112..a7a336947d 100755
--- a/t/t9700-perl-git.sh
+++ b/t/t9700-perl-git.sh
@@ -36,6 +36,7 @@ test_expect_success \
      echo "changed file 1" > file1 &&
      git commit -a -m "second commit" &&
 
+     git config log.mailmap true &&
      git config --add color.test.slot1 green &&
      git config --add test.string value &&
      git config --add test.dupstring value1 &&


There may be issues with other tests.  I didn't do any exhaustive
vetting.

Thanks.