http: refactor options to http_get_*

Over time, the http_get_strbuf function has grown several
optional parameters. We now have a bitfield with multiple
boolean options, as well as an optional strbuf for returning
the content-type of the response. And a future patch in this
series is going to add another strbuf option.

Treating these as separate arguments has a few downsides:

  1. Most call sites need to add extra NULLs and 0s for the
     options they aren't interested in.

  2. The http_get_* functions are actually wrappers around
     2 layers of low-level implementation functions. We have
     to pass these options through individually.

  3. The http_get_strbuf wrapper learned these options, but
     nobody bothered to do so for http_get_file, even though
     it is backed by the same function that does understand
     the options.

Let's consolidate the options into a single struct. For the
common case of the default options, we'll allow callers to
simply pass a NULL for the options struct.

The resulting code is often a few lines longer, but it ends
up being easier to read (and to change as we add new
options, since we do not need to update each call site).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

http.h

@@ -125,11 +125,16 @@ extern void append_remote_object_url(struct strbuf *buf, const char *url,
 extern char *get_remote_object_url(const char *url, const char *hex,
 				   int only_two_digit_prefix);
 
-/* Options for http_request_*() */
-#define HTTP_NO_CACHE		1
-#define HTTP_KEEP_ERROR		2
+/* Options for http_get_*() */
+struct http_get_options {
+	unsigned no_cache:1,
+		 keep_error:1;
 
-/* Return values for http_request_*() */
+	/* If non-NULL, returns the content-type of the response. */
+	struct strbuf *content_type;
+};
+
+/* Return values for http_get_*() */
 #define HTTP_OK			0
 #define HTTP_MISSING_TARGET	1
 #define HTTP_ERROR		2
@@ -142,7 +147,7 @@ extern char *get_remote_object_url(const char *url, const char *hex,
  *
  * If the result pointer is NULL, a HTTP HEAD request is made instead of GET.
  */
-int http_get_strbuf(const char *url, struct strbuf *content_type, struct strbuf *result, int options);
+int http_get_strbuf(const char *url, struct strbuf *result, struct http_get_options *options);
 
 extern int http_fetch_ref(const char *base, struct ref *ref);