log: add --use-mailmap option

Add the --use-mailmap option to log commands. It allows to display
names from mailmap file when displaying logs, whatever the format
used.

Signed-off-by: Antoine Pelisse <apelisse@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-log.txt

@@ -47,6 +47,11 @@ OPTIONS
 	Print out the ref name given on the command line by which each
 	commit was reached.
 
+--use-mailmap::
+	Use mailmap file to map author and committer names and email
+	to canonical real names and email addresses. See
+	linkgit:git-shortlog[1].
+
 --full-diff::
 	Without this flag, "git log -p <path>..." shows commits that
 	touch the specified paths, and diffs about the same specified

builtin/log.c

@@ -22,6 +22,7 @@
 #include "branch.h"
 #include "streaming.h"
 #include "version.h"
+#include "mailmap.h"
 
 /* Set a default date-time format for git log ("log.date" config variable) */
 static const char *default_date_mode = NULL;
@@ -94,11 +95,12 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 			 struct rev_info *rev, struct setup_revision_opt *opt)
 {
 	struct userformat_want w;
-	int quiet = 0, source = 0;
+	int quiet = 0, source = 0, mailmap = 0;
 
 	const struct option builtin_log_options[] = {
 		OPT_BOOLEAN(0, "quiet", &quiet, N_("suppress diff output")),
 		OPT_BOOLEAN(0, "source", &source, N_("show source")),
+		OPT_BOOLEAN(0, "use-mailmap", &mailmap, N_("Use mail map file")),
 		{ OPTION_CALLBACK, 0, "decorate", NULL, NULL, N_("decorate options"),
 		  PARSE_OPT_OPTARG, decorate_callback},
 		OPT_END()
@@ -136,6 +138,11 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 	if (source)
 		rev->show_source = 1;
 
+	if (mailmap) {
+		rev->mailmap = xcalloc(1, sizeof(struct string_list));
+		read_mailmap(rev->mailmap, NULL);
+	}
+
 	if (rev->pretty_given && rev->commit_format == CMIT_FMT_RAW) {
 		/*
 		 * "log --pretty=raw" is special; ignore UI oriented