Skip cache slot when time-to-live is zero

If time-to-live is set to zero, we don't need to regenerate the cache
slots on every request. Instead, just skip the caching process and
immediately provide the dynamically generated version of the page.
Setting time-to-live to zero is useful when you want to disable caching
for certain pages.

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>

cache.c

@@ -343,7 +343,7 @@ int cache_process(int size, const char *path, const char *key, int ttl,
 	int result;
 
 	/* If the cache is disabled, just generate the content */
-	if (size <= 0) {
+	if (size <= 0 || ttl == 0) {
 		fn();
 		return 0;
 	}

cgitrc.5.txt

@@ -61,37 +61,43 @@ cache-root::
 cache-static-ttl::
 	Number which specifies the time-to-live, in minutes, for the cached
 	version of repository pages accessed with a fixed SHA1. Negative
-	values have infinite ttl. Default value: -1".
+	values have infinite ttl, zero means that the cache is disabled for
+	this type of pages. Default value: -1".
 
 cache-dynamic-ttl::
 	Number which specifies the time-to-live, in minutes, for the cached
 	version of repository pages accessed without a fixed SHA1. Negative
-	values have infinite ttl. Default value: "5".
+	values have infinite ttl, zero means that the cache is disabled for this
+	type of pages. Default value: "5".
 
 cache-repo-ttl::
 	Number which specifies the time-to-live, in minutes, for the cached
 	version of the repository summary page. Negative values have infinite
-	ttl. Default value: "5".
+	ttl, zero means that the cache is disabled for this type of pages.
+	Default value: "5".
 
 cache-root-ttl::
 	Number which specifies the time-to-live, in minutes, for the cached
 	version of the repository index page. Negative values have infinite
-	ttl. Default value: "5".
+	ttl, zero means that the cache is disabled for this type of pages.
+	Default value: "5".
 
 cache-scanrc-ttl::
 	Number which specifies the time-to-live, in minutes, for the result
 	of scanning a path for git repositories. Negative values have infinite
-	ttl. Default value: "15".
+	ttl, zero means that the cache is disable for this type of pages.
+	Default value: "15".
 
 cache-about-ttl::
 	Number which specifies the time-to-live, in minutes, for the cached
 	version of the repository about page. Negative values have infinite
-	ttl. Default value: "15".
+	ttl, zero means that the cache is disable for this type of pages.
+	Default value: "15".
 
 cache-snapshot-ttl::
 	Number which specifies the time-to-live, in minutes, for the cached
-	version of snapshots. Negative values have infinite ttl. Default
-	value: "5".
+	version of snapshots. Negative values have infinite ttl, zero means
+	that the cache is disable for this type of pages. Default value: "5".
 
 cache-size::
 	The maximum number of entries in the cgit cache. Default value: "0"