Modularize commit-walker

This turns the extern functions to be provided by the backend into a
struct of pointers, renames the functions to be more
namespace-friendly, and updates http-fetch to this interface. It
removes the unused include from http-push.c. It makes git-http-fetch a
builtin (with the implementation a separate file, accessible
directly).

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-http-fetch.c

@@ -0,0 +1,77 @@
+#include "cache.h"
+#include "walker.h"
+
+int cmd_http_fetch(int argc, const char **argv, const char *prefix)
+{
+	struct walker *walker;
+	int commits_on_stdin = 0;
+	int commits;
+	const char **write_ref = NULL;
+	char **commit_id;
+	const char *url;
+	int arg = 1;
+	int rc = 0;
+	int get_tree = 0;
+	int get_history = 0;
+	int get_all = 0;
+	int get_verbosely = 0;
+	int get_recover = 0;
+
+	git_config(git_default_config);
+
+	while (arg < argc && argv[arg][0] == '-') {
+		if (argv[arg][1] == 't') {
+			get_tree = 1;
+		} else if (argv[arg][1] == 'c') {
+			get_history = 1;
+		} else if (argv[arg][1] == 'a') {
+			get_all = 1;
+			get_tree = 1;
+			get_history = 1;
+		} else if (argv[arg][1] == 'v') {
+			get_verbosely = 1;
+		} else if (argv[arg][1] == 'w') {
+			write_ref = &argv[arg + 1];
+			arg++;
+		} else if (!strcmp(argv[arg], "--recover")) {
+			get_recover = 1;
+		} else if (!strcmp(argv[arg], "--stdin")) {
+			commits_on_stdin = 1;
+		}
+		arg++;
+	}
+	if (argc < arg + 2 - commits_on_stdin) {
+		usage("git-http-fetch [-c] [-t] [-a] [-v] [--recover] [-w ref] [--stdin] commit-id url");
+		return 1;
+	}
+	if (commits_on_stdin) {
+		commits = walker_targets_stdin(&commit_id, &write_ref);
+	} else {
+		commit_id = (char **) &argv[arg++];
+		commits = 1;
+	}
+	url = argv[arg];
+
+	walker = get_http_walker(url);
+	walker->get_tree = get_tree;
+	walker->get_history = get_history;
+	walker->get_all = get_all;
+	walker->get_verbosely = get_verbosely;
+	walker->get_recover = get_recover;
+
+	rc = walker_fetch(walker, commits, commit_id, write_ref, url);
+
+	if (commits_on_stdin)
+		walker_targets_free(commits, commit_id, write_ref);
+
+	if (walker->corrupt_object_found) {
+		fprintf(stderr,
+"Some loose object were found to be corrupt, but they might be just\n"
+"a false '404 Not Found' error message sent with incorrect HTTP\n"
+"status code.  Suggest running git-fsck.\n");
+	}
+
+	walker_free(walker);
+
+	return rc;
+}