[PATCH 2/4] pager: refactor `pager_command_config()`

["Martin Ågren" <martin.agren@gmail.com>]

`pager_command_config()` checks for the config `pager.<cmd>`. In the
next commit, we will want to also look for some strings on the form
`pager.<cmd>.foo`.

Refactor the code to verify upfront that the string starts with
"pager.<cmd>" and then check that the remainder is the empty string.
This makes it easy to look for other remainders in the next patch.

While at it, before assigning to `value`, free any old value we might
already have picked up.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
---
 pager.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/pager.c b/pager.c
index 92b23e6cd..8968f26f1 100644
--- a/pager.c
+++ b/pager.c
@@ -191,14 +191,19 @@ struct pager_command_config_data {
 static int pager_command_config(const char *var, const char *value, void *vdata)
 {
 	struct pager_command_config_data *data = vdata;
-	const char *cmd;
+	const char *cmd, *remainder;
+
+	if (!skip_prefix(var, "pager.", &cmd) ||
+	    !skip_prefix(cmd, data->cmd, &remainder))
+		return 0;
 
-	if (skip_prefix(var, "pager.", &cmd) && !strcmp(cmd, data->cmd)) {
+	if (!*remainder) {
 		int b = git_parse_maybe_bool(value);
 		if (b >= 0)
 			data->want = b;
 		else {
 			data->want = 1;
+			free(data->value);
 			data->value = xstrdup(value);
 		}
 	}
-- 
2.15.0.415.gac1375d7e