[PATCH 3/6] convert some config callbacks to match_config_key

[Jeff King <peff@peff.net>]

This is easier to read and avoids magic offset constants
which need to be in sync with the section-name we provide.

Signed-off-by: Jeff King <peff@peff.net>
---
 convert.c  |  6 +-----
 ll-merge.c |  6 +-----
 userdiff.c | 13 +++----------
 3 files changed, 5 insertions(+), 20 deletions(-)

diff --git a/convert.c b/convert.c
index 6602155..e3ecb30 100644
--- a/convert.c
+++ b/convert.c
@@ -465,10 +465,8 @@ static int read_convert_config(const char *var, const char *value, void *cb)
 	 * External conversion drivers are configured using
 	 * "filter.<name>.variable".
 	 */
-	if (prefixcmp(var, "filter.") || (ep = strrchr(var, '.')) == var + 6)
+	if (match_config_key(var, "filter", &name, &namelen, &ep) < 0 || !name)
 		return 0;
-	name = var + 7;
-	namelen = ep - name;
 	for (drv = user_convert; drv; drv = drv->next)
 		if (!strncmp(drv->name, name, namelen) && !drv->name[namelen])
 			break;
@@ -479,8 +477,6 @@ static int read_convert_config(const char *var, const char *value, void *cb)
 		user_convert_tail = &(drv->next);
 	}
 
-	ep++;
-
 	/*
 	 * filter.<name>.smudge and filter.<name>.clean specifies
 	 * the command line:
diff --git a/ll-merge.c b/ll-merge.c
index acea33b..d4c4ff6 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -236,15 +236,13 @@ static int read_merge_config(const char *var, const char *value, void *cb)
 	 * especially, we do not want to look at variables such as
 	 * "merge.summary", "merge.tool", and "merge.verbosity".
 	 */
-	if (prefixcmp(var, "merge.") || (ep = strrchr(var, '.')) == var + 5)
+	if (match_config_key(var, "merge", &name, &namelen, &ep) < 0 || !name)
 		return 0;
 
 	/*
 	 * Find existing one as we might be processing merge.<name>.var2
 	 * after seeing merge.<name>.var1.
 	 */
-	name = var + 6;
-	namelen = ep - name;
 	for (fn = ll_user_merge; fn; fn = fn->next)
 		if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
 			break;
@@ -256,8 +254,6 @@ static int read_merge_config(const char *var, const char *value, void *cb)
 		ll_user_merge_tail = &(fn->next);
 	}
 
-	ep++;
-
 	if (!strcmp("name", ep)) {
 		if (!value)
 			return error("%s: lacks value", var);
diff --git a/userdiff.c b/userdiff.c
index ed958ef..1a6a0fa 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -188,20 +188,13 @@ static struct userdiff_driver *parse_driver(const char *var,
 		const char *value, const char *type)
 {
 	struct userdiff_driver *drv;
-	const char *dot;
-	const char *name;
+	const char *name, *key;
 	int namelen;
 
-	if (prefixcmp(var, "diff."))
-		return NULL;
-	dot = strrchr(var, '.');
-	if (dot == var + 4)
-		return NULL;
-	if (strcmp(type, dot+1))
+	if (match_config_key(var, "diff", &name, &namelen, &key) < 0 ||
+	    strcmp(type, key))
 		return NULL;
 
-	name = var + 5;
-	namelen = dot - name;
 	drv = userdiff_find_by_namelen(name, namelen);
 	if (!drv) {
 		ALLOC_GROW(drivers, ndrivers+1, drivers_alloc);
-- 
1.8.1.rc1.10.g7d71f7b