allow command-specific pagers in pager.<cmd>

A user may want different pager settings or even a
different pager for various subcommands (e.g., because they
use different less settings for "log" vs "diff", or because
they have a pager that interprets only log output but not
other commands).

This patch extends the pager.<cmd> syntax to support not
only boolean to-page-or-not-to-page, but also to specify a
pager just for a specific command.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1521,11 +1521,13 @@ pack.packSizeLimit::
 	supported.
 
 pager.<cmd>::
-	Allows turning on or off pagination of the output of a
-	particular git subcommand when writing to a tty.  If
-	`\--paginate` or `\--no-pager` is specified on the command line,
-	it takes precedence over this option.  To disable pagination for
-	all commands, set `core.pager` or `GIT_PAGER` to `cat`.
+	If the value is boolean, turns on or off pagination of the
+	output of a particular git subcommand when writing to a tty.
+	Otherwise, turns on pagination for the subcommand using the
+	pager specified by the value of `pager.<cmd>`.  If `\--paginate`
+	or `\--no-pager` is specified on the command line, it takes
+	precedence over this option.  To disable pagination for all
+	commands, set `core.pager` or `GIT_PAGER` to `cat`.
 
 pretty.<name>::
 	Alias for a --pretty= format string, as specified in

git.c

@@ -19,14 +19,22 @@ static struct startup_info git_startup_info;
 static int use_pager = -1;
 struct pager_config {
 	const char *cmd;
-	int val;
+	int want;
+	char *value;
 };
 
 static int pager_command_config(const char *var, const char *value, void *data)
 {
 	struct pager_config *c = data;
-	if (!prefixcmp(var, "pager.") && !strcmp(var + 6, c->cmd))
-		c->val = git_config_bool(var, value);
+	if (!prefixcmp(var, "pager.") && !strcmp(var + 6, c->cmd)) {
+		int b = git_config_maybe_bool(var, value);
+		if (b >= 0)
+			c->want = b;
+		else {
+			c->want = 1;
+			c->value = xstrdup(value);
+		}
+	}
 	return 0;
 }
 
@@ -35,9 +43,12 @@ int check_pager_config(const char *cmd)
 {
 	struct pager_config c;
 	c.cmd = cmd;
-	c.val = -1;
+	c.want = -1;
+	c.value = NULL;
 	git_config(pager_command_config, &c);
-	return c.val;
+	if (c.value)
+		pager_program = c.value;
+	return c.want;
 }
 
 static void commit_pager_choice(void) {

t/t7006-pager.sh

@@ -435,4 +435,33 @@ test_core_pager_subdir    expect_success 'git -p shortlog'
 test_core_pager_subdir    expect_success test_must_fail \
 					 'git -p apply </dev/null'
 
+test_expect_success TTY 'command-specific pager' '
+	unset PAGER GIT_PAGER;
+	echo "foo:initial" >expect &&
+	>actual &&
+	git config --unset core.pager &&
+	git config pager.log "sed s/^/foo:/ >actual" &&
+	test_terminal git log --format=%s -1 &&
+	test_cmp expect actual
+'
+
+test_expect_success TTY 'command-specific pager overrides core.pager' '
+	unset PAGER GIT_PAGER;
+	echo "foo:initial" >expect &&
+	>actual &&
+	git config core.pager "exit 1"
+	git config pager.log "sed s/^/foo:/ >actual" &&
+	test_terminal git log --format=%s -1 &&
+	test_cmp expect actual
+'
+
+test_expect_success TTY 'command-specific pager overridden by environment' '
+	GIT_PAGER="sed s/^/foo:/ >actual" && export GIT_PAGER &&
+	>actual &&
+	echo "foo:initial" >expect &&
+	git config pager.log "exit 1" &&
+	test_terminal git log --format=%s -1 &&
+	test_cmp expect actual
+'
+
 test_done