Merge branch 'fm/fetch-raw-sha1'

"git upload-pack" that serves "git fetch" can be told to serve
commits that are not at the tip of any ref, as long as they are
reachable from a ref, with uploadpack.allowReachableSHA1InWant
configuration variable.

* fm/fetch-raw-sha1:
  upload-pack: optionally allow fetching reachable sha1
  upload-pack: prepare to extend allow-tip-sha1-in-want
  config.txt: clarify allowTipSHA1InWant with camelCase

Author: gitster

Documentation/config.txt

@@ -2558,14 +2558,20 @@ uploadpack.hideRefs::
 	are under the hierarchies listed on the value of this
 	variable is excluded, and is hidden from `git ls-remote`,
 	`git fetch`, etc.  An attempt to fetch a hidden ref by `git
-	fetch` will fail.  See also `uploadpack.allowtipsha1inwant`.
+	fetch` will fail.  See also `uploadpack.allowTipSHA1InWant`.
 
-uploadpack.allowtipsha1inwant::
+uploadpack.allowTipSHA1InWant::
 	When `uploadpack.hideRefs` is in effect, allow `upload-pack`
 	to accept a fetch request that asks for an object at the tip
 	of a hidden ref (by default, such a request is rejected).
 	see also `uploadpack.hideRefs`.
 
+uploadpack.allowReachableSHA1InWant::
+	Allow `upload-pack` to accept a fetch request that asks for an
+	object that is reachable from any ref tip. However, note that
+	calculating object reachability is computationally expensive.
+	Defaults to `false`.
+
 uploadpack.keepAlive::
 	When `upload-pack` has started `pack-objects`, there may be a
 	quiet period while `pack-objects` prepares the pack. Normally

Documentation/technical/http-protocol.txt

@@ -319,7 +319,8 @@ Servers SHOULD support all capabilities defined here.
 Clients MUST send at least one "want" command in the request body.
 Clients MUST NOT reference an id in a "want" command which did not
 appear in the response obtained through ref discovery unless the
-server advertises capability `allow-tip-sha1-in-want`.
+server advertises capability `allow-tip-sha1-in-want` or
+`allow-reachable-sha1-in-want`.
 
   compute_request   =  want_list
 		       have_list

Documentation/technical/protocol-capabilities.txt

@@ -260,6 +260,13 @@ If the upload-pack server advertises this capability, fetch-pack may
 send "want" lines with SHA-1s that exist at the server but are not
 advertised by upload-pack.
 
+allow-reachable-sha1-in-want
+----------------------------
+
+If the upload-pack server advertises this capability, fetch-pack may
+send "want" lines with SHA-1s that exist at the server but are not
+advertised by upload-pack.
+
 push-cert=<nonce>
 -----------------
 

fetch-pack.c

@@ -43,7 +43,12 @@ static int marked;
 #define MAX_IN_VAIN 256
 
 static struct prio_queue rev_list = { compare_commits_by_commit_date };
-static int non_common_revs, multi_ack, use_sideband, allow_tip_sha1_in_want;
+static int non_common_revs, multi_ack, use_sideband;
+/* Allow specifying sha1 if it is a ref tip. */
+#define ALLOW_TIP_SHA1	01
+/* Allow request of a sha1 if it is reachable from a ref (possibly hidden ref). */
+#define ALLOW_REACHABLE_SHA1	02
+static unsigned int allow_unadvertised_object_request;
 
 static void rev_list_push(struct commit *commit, int mark)
 {
@@ -542,7 +547,8 @@ static void filter_refs(struct fetch_pack_args *args,
 	}
 
 	/* Append unmatched requests to the list */
-	if (allow_tip_sha1_in_want) {
+	if ((allow_unadvertised_object_request &
+	    (ALLOW_TIP_SHA1 | ALLOW_REACHABLE_SHA1))) {
 		for (i = 0; i < nr_sought; i++) {
 			unsigned char sha1[20];
 
@@ -821,7 +827,12 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	if (server_supports("allow-tip-sha1-in-want")) {
 		if (args->verbose)
 			fprintf(stderr, "Server supports allow-tip-sha1-in-want\n");
-		allow_tip_sha1_in_want = 1;
+		allow_unadvertised_object_request |= ALLOW_TIP_SHA1;
+	}
+	if (server_supports("allow-reachable-sha1-in-want")) {
+		if (args->verbose)
+			fprintf(stderr, "Server supports allow-reachable-sha1-in-want\n");
+		allow_unadvertised_object_request |= ALLOW_REACHABLE_SHA1;
 	}
 	if (!server_supports("thin-pack"))
 		args->use_thin_pack = 0;

t/t5516-fetch-push.sh

@@ -1120,6 +1120,61 @@ test_expect_success 'fetch exact SHA1' '
 	)
 '
 
+for configallowtipsha1inwant in true false
+do
+	test_expect_success "shallow fetch reachable SHA1 (but not a ref), allowtipsha1inwant=$configallowtipsha1inwant" '
+		mk_empty testrepo &&
+		(
+			cd testrepo &&
+			git config uploadpack.allowtipsha1inwant $configallowtipsha1inwant &&
+			git commit --allow-empty -m foo &&
+			git commit --allow-empty -m bar
+		) &&
+		SHA1=$(git --git-dir=testrepo/.git rev-parse HEAD^) &&
+		mk_empty shallow &&
+		(
+			cd shallow &&
+			test_must_fail git fetch --depth=1 ../testrepo/.git $SHA1 &&
+			git --git-dir=../testrepo/.git config uploadpack.allowreachablesha1inwant true &&
+			git fetch --depth=1 ../testrepo/.git $SHA1 &&
+			git cat-file commit $SHA1
+		)
+	'
+
+	test_expect_success "deny fetch unreachable SHA1, allowtipsha1inwant=$configallowtipsha1inwant" '
+		mk_empty testrepo &&
+		(
+			cd testrepo &&
+			git config uploadpack.allowtipsha1inwant $configallowtipsha1inwant &&
+			git commit --allow-empty -m foo &&
+			git commit --allow-empty -m bar &&
+			git commit --allow-empty -m xyz
+		) &&
+		SHA1_1=$(git --git-dir=testrepo/.git rev-parse HEAD^^) &&
+		SHA1_2=$(git --git-dir=testrepo/.git rev-parse HEAD^) &&
+		SHA1_3=$(git --git-dir=testrepo/.git rev-parse HEAD) &&
+		(
+			cd testrepo &&
+			git reset --hard $SHA1_2 &&
+			git cat-file commit $SHA1_1 &&
+			git cat-file commit $SHA1_3
+		) &&
+		mk_empty shallow &&
+		(
+			cd shallow &&
+			test_must_fail git fetch ../testrepo/.git $SHA1_3 &&
+			test_must_fail git fetch ../testrepo/.git $SHA1_1 &&
+			git --git-dir=../testrepo/.git config uploadpack.allowreachablesha1inwant true &&
+			git fetch ../testrepo/.git $SHA1_1 &&
+			git cat-file commit $SHA1_1 &&
+			test_must_fail git cat-file commit $SHA1_2 &&
+			git fetch ../testrepo/.git $SHA1_2 &&
+			git cat-file commit $SHA1_2 &&
+			test_must_fail git fetch ../testrepo/.git $SHA1_3
+		)
+	'
+done
+
 test_expect_success 'fetch follows tags by default' '
 	mk_test testrepo heads/master &&
 	rm -fr src dst &&

upload-pack.c

@@ -35,7 +35,11 @@ static int multi_ack;
 static int no_done;
 static int use_thin_pack, use_ofs_delta, use_include_tag;
 static int no_progress, daemon_mode;
-static int allow_tip_sha1_in_want;
+/* Allow specifying sha1 if it is a ref tip. */
+#define ALLOW_TIP_SHA1	01
+/* Allow request of a sha1 if it is reachable from a ref (possibly hidden ref). */
+#define ALLOW_REACHABLE_SHA1	02
+static unsigned int allow_unadvertised_object_request;
 static int shallow_nr;
 static struct object_array have_obj;
 static struct object_array want_obj;
@@ -442,8 +446,9 @@ static int get_common_commits(void)
 
 static int is_our_ref(struct object *o)
 {
-	return o->flags &
-		((allow_tip_sha1_in_want ? HIDDEN_REF : 0) | OUR_REF);
+	int allow_hidden_ref = (allow_unadvertised_object_request &
+			(ALLOW_TIP_SHA1 | ALLOW_REACHABLE_SHA1));
+	return o->flags & ((allow_hidden_ref ? HIDDEN_REF : 0) | OUR_REF);
 }
 
 static void check_non_tip(void)
@@ -456,8 +461,12 @@ static void check_non_tip(void)
 	char namebuf[42]; /* ^ + SHA-1 + LF */
 	int i;
 
-	/* In the normal in-process case non-tip request can never happen */
-	if (!stateless_rpc)
+	/*
+	 * In the normal in-process case without
+	 * uploadpack.allowReachableSHA1InWant,
+	 * non-tip requests can never happen.
+	 */
+	if (!stateless_rpc && !(allow_unadvertised_object_request & ALLOW_REACHABLE_SHA1))
 		goto error;
 
 	cmd.argv = argv;
@@ -724,10 +733,13 @@ static int send_ref(const char *refname, const unsigned char *sha1, int flag, vo
 		struct strbuf symref_info = STRBUF_INIT;
 
 		format_symref_info(&symref_info, cb_data);
-		packet_write(1, "%s %s%c%s%s%s%s agent=%s\n",
+		packet_write(1, "%s %s%c%s%s%s%s%s agent=%s\n",
 			     sha1_to_hex(sha1), refname_nons,
 			     0, capabilities,
-			     allow_tip_sha1_in_want ? " allow-tip-sha1-in-want" : "",
+			     (allow_unadvertised_object_request & ALLOW_TIP_SHA1) ?
+				     " allow-tip-sha1-in-want" : "",
+			     (allow_unadvertised_object_request & ALLOW_REACHABLE_SHA1) ?
+				     " allow-reachable-sha1-in-want" : "",
 			     stateless_rpc ? " no-done" : "",
 			     symref_info.buf,
 			     git_user_agent_sanitized());
@@ -787,9 +799,17 @@ static void upload_pack(void)
 
 static int upload_pack_config(const char *var, const char *value, void *unused)
 {
-	if (!strcmp("uploadpack.allowtipsha1inwant", var))
-		allow_tip_sha1_in_want = git_config_bool(var, value);
-	else if (!strcmp("uploadpack.keepalive", var)) {
+	if (!strcmp("uploadpack.allowtipsha1inwant", var)) {
+		if (git_config_bool(var, value))
+			allow_unadvertised_object_request |= ALLOW_TIP_SHA1;
+		else
+			allow_unadvertised_object_request &= ~ALLOW_TIP_SHA1;
+	} else if (!strcmp("uploadpack.allowreachablesha1inwant", var)) {
+		if (git_config_bool(var, value))
+			allow_unadvertised_object_request |= ALLOW_REACHABLE_SHA1;
+		else
+			allow_unadvertised_object_request &= ~ALLOW_REACHABLE_SHA1;
+	} else if (!strcmp("uploadpack.keepalive", var)) {
 		keepalive = git_config_int(var, value);
 		if (!keepalive)
 			keepalive = -1;