format-patch: format.from gives the default for --from

This helps users who would prefer format-patch to default to --from,
and makes it easier to change the default in the future.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1227,6 +1227,16 @@ format.attach::
 	value as the boundary.  See the --attach option in
 	linkgit:git-format-patch[1].
 
+format.from::
+	Provides the default value for the `--from` option to format-patch.
+	Accepts a boolean value, or a name and email address.  If false,
+	format-patch defaults to `--no-from`, using commit authors directly in
+	the "From:" field of patch mails.  If true, format-patch defaults to
+	`--from`, using your committer identity in the "From:" field of patch
+	mails and including a "From:" field in the body of the patch mail if
+	different.  If set to a non-boolean value, format-patch uses that
+	value instead of your committer identity.  Defaults to false.
+
 format.numbered::
 	A boolean which can enable or disable sequence numbers in patch
 	subjects.  It defaults to "auto" which enables it only if there

builtin/log.c

@@ -703,6 +703,7 @@ static void add_header(const char *value)
 static int thread;
 static int do_signoff;
 static int base_auto;
+static char *from;
 static const char *signature = git_version_string;
 static const char *signature_file;
 static int config_cover_letter;
@@ -791,6 +792,17 @@ static int git_format_config(const char *var, const char *value, void *cb)
 		base_auto = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "format.from")) {
+		int b = git_config_maybe_bool(var, value);
+		free(from);
+		if (b < 0)
+			from = xstrdup(value);
+		else if (b)
+			from = xstrdup(git_committer_info(IDENT_NO_DATE));
+		else
+			from = NULL;
+		return 0;
+	}
 
 	return git_log_config(var, value, cb);
 }
@@ -1368,7 +1380,6 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	int quiet = 0;
 	int reroll_count = -1;
 	char *branch_name = NULL;
-	char *from = NULL;
 	char *base_commit = NULL;
 	struct base_tree_info bases;
 

contrib/completion/git-completion.bash

@@ -2085,6 +2085,7 @@ _git_config ()
 		format.attach
 		format.cc
 		format.coverLetter
+		format.from
 		format.headers
 		format.numbered
 		format.pretty

t/t4014-format-patch.sh

@@ -229,6 +229,46 @@ check_patch () {
 	grep -e "^Subject:" "$1"
 }
 
+test_expect_success 'format.from=false' '
+
+	git -c format.from=false format-patch --stdout master..side |
+	sed -e "/^\$/q" >patch &&
+	check_patch patch &&
+	! grep "^From: C O Mitter <committer@example.com>\$" patch
+'
+
+test_expect_success 'format.from=true' '
+
+	git -c format.from=true format-patch --stdout master..side |
+	sed -e "/^\$/q" >patch &&
+	check_patch patch &&
+	grep "^From: C O Mitter <committer@example.com>\$" patch
+'
+
+test_expect_success 'format.from with address' '
+
+	git -c format.from="F R Om <from@example.com>" format-patch --stdout master..side |
+	sed -e "/^\$/q" >patch &&
+	check_patch patch &&
+	grep "^From: F R Om <from@example.com>\$" patch
+'
+
+test_expect_success '--no-from overrides format.from' '
+
+	git -c format.from="F R Om <from@example.com>" format-patch --no-from --stdout master..side |
+	sed -e "/^\$/q" >patch &&
+	check_patch patch &&
+	! grep "^From: F R Om <from@example.com>\$" patch
+'
+
+test_expect_success '--from overrides format.from' '
+
+	git -c format.from="F R Om <from@example.com>" format-patch --from --stdout master..side |
+	sed -e "/^\$/q" >patch &&
+	check_patch patch &&
+	! grep "^From: F R Om <from@example.com>\$" patch
+'
+
 test_expect_success '--no-to overrides config.to' '
 
 	git config --replace-all format.to \