log.decorate: usability fixes

The configuration is meant to suppliment --decorate command line option
that can be used as a boolean to turn the feature on, so it is natural
to expect

	[log]
		decorate
		decorate = yes

to work.  The original commit would segfault with the first one, and
would not understand the second one.

Once a user has this configuration in ~/.gitconfig, there needs to be a
way to override it from the command line.  Add --no-decorate option to
log family and also allow --decorate=no to mean the same thing.  Since
we allow setting log.decorate to 'true', the command line also should
accept --decorate=yes and behave accordingly.

New tests in t4202 are designed to exercise the interaction between the
configuration variable and the command line option that overrides it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-log.txt

@@ -37,7 +37,8 @@ include::diff-options.txt[]
 	and <until>, see "SPECIFYING REVISIONS" section in
 	linkgit:git-rev-parse[1].
 
---decorate[=short|full]::
+--no-decorate::
+--decorate[=short|full|no]::
 	Print out the ref names of any commits that are shown. If 'short' is
 	specified, the ref name prefixes 'refs/heads/', 'refs/tags/' and
 	'refs/remotes/' will not be printed. If 'full' is specified, the

builtin-log.c

@@ -24,14 +24,31 @@
 static const char *default_date_mode = NULL;
 
 static int default_show_root = 1;
-static int decoration_style = 0;
+static int decoration_style;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static const char *fmt_pretty;
 
 static const char * const builtin_log_usage =
 	"git log [<options>] [<since>..<until>] [[--] <path>...]\n"
 	"   or: git show [options] <object>...";
 
+static int parse_decoration_style(const char *var, const char *value)
+{
+	switch (git_config_maybe_bool(var, value)) {
+	case 1:
+		return DECORATE_SHORT_REFS;
+	case 0:
+		return 0;
+	default:
+		break;
+	}
+	if (!strcmp(value, "full"))
+		return DECORATE_FULL_REFS;
+	else if (!strcmp(value, "short"))
+		return DECORATE_SHORT_REFS;
+	return -1;
+}
+
 static void cmd_log_init(int argc, const char **argv, const char *prefix,
 		      struct rev_info *rev)
 {
@@ -74,12 +91,11 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
 			decoration_style = DECORATE_SHORT_REFS;
 		} else if (!prefixcmp(arg, "--decorate=")) {
 			const char *v = skip_prefix(arg, "--decorate=");
-			if (!strcmp(v, "full"))
-				decoration_style = DECORATE_FULL_REFS;
-			else if (!strcmp(v, "short"))
-				decoration_style = DECORATE_SHORT_REFS;
-			else
+			decoration_style = parse_decoration_style(arg, v);
+			if (decoration_style < 0)
 				die("invalid --decorate option: %s", arg);
+		} else if (!strcmp(arg, "--no-decorate")) {
+			decoration_style = 0;
 		} else if (!strcmp(arg, "--source")) {
 			rev->show_source = 1;
 		} else if (!strcmp(arg, "-h")) {
@@ -253,10 +269,9 @@ static int git_log_config(const char *var, const char *value, void *cb)
 	if (!strcmp(var, "log.date"))
 		return git_config_string(&default_date_mode, var, value);
 	if (!strcmp(var, "log.decorate")) {
-		if (!strcmp(value, "full"))
-			decoration_style = DECORATE_FULL_REFS;
-		else if (!strcmp(value, "short"))
-			decoration_style = DECORATE_SHORT_REFS;
+		decoration_style = parse_decoration_style(var, value);
+		if (decoration_style < 0)
+			decoration_style = 0; /* maybe warn? */
 		return 0;
 	}
 	if (!strcmp(var, "log.showroot")) {

t/t4202-log.sh

@@ -387,5 +387,54 @@ test_expect_success 'log --graph with merge' '
 	test_cmp expect actual
 '
 
+test_expect_success 'log.decorate configuration' '
+	git config --unset-all log.decorate || :
+
+	git log --oneline >expect.none &&
+	git log --oneline --decorate >expect.short &&
+	git log --oneline --decorate=full >expect.full &&
+
+	echo "[log] decorate" >>.git/config &&
+	git log --oneline >actual &&
+	test_cmp expect.short actual &&
+
+	git config --unset-all log.decorate &&
+	git config log.decorate true &&
+	git log --oneline >actual &&
+	test_cmp expect.short actual &&
+	git log --oneline --decorate=full >actual &&
+	test_cmp expect.full actual &&
+	git log --oneline --decorate=no >actual &&
+	test_cmp expect.none actual &&
+
+	git config --unset-all log.decorate &&
+	git config log.decorate no &&
+	git log --oneline >actual &&
+	test_cmp expect.none actual &&
+	git log --oneline --decorate >actual &&
+	test_cmp expect.short actual &&
+	git log --oneline --decorate=full >actual &&
+	test_cmp expect.full actual &&
+
+	git config --unset-all log.decorate &&
+	git config log.decorate short &&
+	git log --oneline >actual &&
+	test_cmp expect.short actual &&
+	git log --oneline --no-decorate >actual &&
+	test_cmp expect.none actual &&
+	git log --oneline --decorate=full >actual &&
+	test_cmp expect.full actual &&
+
+	git config --unset-all log.decorate &&
+	git config log.decorate full &&
+	git log --oneline >actual &&
+	test_cmp expect.full actual &&
+	git log --oneline --no-decorate >actual &&
+	test_cmp expect.none actual &&
+	git log --oneline --decorate >actual &&
+	test_cmp expect.short actual
+
+'
+
 test_done