Merge branch 'js/ref-namespaces'

* js/ref-namespaces:
  ref namespaces: tests
  ref namespaces: documentation
  ref namespaces: Support remote repositories via upload-pack and receive-pack
  ref namespaces: infrastructure
  Fix prefix handling in ref iteration functions

Documentation/Makefile

@@ -6,7 +6,7 @@ MAN5_TXT=gitattributes.txt gitignore.txt gitmodules.txt githooks.txt \
 	gitrepository-layout.txt
 MAN7_TXT=gitcli.txt gittutorial.txt gittutorial-2.txt \
 	gitcvs-migration.txt gitcore-tutorial.txt gitglossary.txt \
-	gitdiffcore.txt gitrevisions.txt gitworkflows.txt
+	gitdiffcore.txt gitnamespaces.txt gitrevisions.txt gitworkflows.txt
 
 MAN_TXT = $(MAN1_TXT) $(MAN5_TXT) $(MAN7_TXT)
 MAN_XML=$(patsubst %.txt,%.xml,$(MAN_TXT))

Documentation/git-http-backend.txt

@@ -119,6 +119,14 @@ ScriptAliasMatch \
 
 ScriptAlias /git/ /var/www/cgi-bin/gitweb.cgi/
 ----------------------------------------------------------------
++
+To serve multiple repositories from different linkgit:gitnamespaces[7] in a
+single repository:
++
+----------------------------------------------------------------
+SetEnvIf Request_URI "^/git/([^/]*)" GIT_NAMESPACE=$1
+ScriptAliasMatch ^/git/[^/]*(.*) /usr/libexec/git-core/git-http-backend/storage.git$1
+----------------------------------------------------------------
 
 Accelerated static Apache 2.x::
 	Similar to the above, but Apache can be used to return static

Documentation/git-receive-pack.txt

@@ -153,7 +153,7 @@ if the repository is packed and is served via a dumb transport.
 
 SEE ALSO
 --------
-linkgit:git-send-pack[1]
+linkgit:git-send-pack[1], linkgit:gitnamespaces[7]
 
 GIT
 ---

Documentation/git-upload-pack.txt

@@ -34,6 +34,10 @@ OPTIONS
 <directory>::
 	The repository to sync from.
 
+SEE ALSO
+--------
+linkgit:gitnamespaces[7]
+
 GIT
 ---
 Part of the linkgit:git[1] suite

Documentation/git.txt

@@ -10,8 +10,8 @@ SYNOPSIS
 --------
 [verse]
 'git' [--version] [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
-    [-p|--paginate|--no-pager] [--no-replace-objects]
-    [--bare] [--git-dir=<path>] [--work-tree=<path>]
+    [-p|--paginate|--no-pager] [--no-replace-objects] [--bare]
+    [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
     [-c <name>=<value>]
     [--help] <command> [<args>]
 
@@ -330,6 +330,11 @@ help ...`.
 	variable (see core.worktree in linkgit:git-config[1] for a
 	more detailed discussion).
 
+--namespace=<path>::
+	Set the git namespace.  See linkgit:gitnamespaces[7] for more
+	details.  Equivalent to setting the `GIT_NAMESPACE` environment
+	variable.
+
 --bare::
 	Treat the repository as a bare repository.  If GIT_DIR
 	environment is not set, it is set to the current working
@@ -593,6 +598,10 @@ git so take care if using Cogito etc.
 	This can also be controlled by the '--work-tree' command line
 	option and the core.worktree configuration variable.
 
+'GIT_NAMESPACE'::
+	Set the git namespace; see linkgit:gitnamespaces[7] for details.
+	The '--namespace' command-line option also sets this value.
+
 'GIT_CEILING_DIRECTORIES'::
 	This should be a colon-separated list of absolute paths.
 	If set, it is a list of directories that git should not chdir

Documentation/gitnamespaces.txt

@@ -0,0 +1,75 @@
+gitnamespaces(7)
+================
+
+NAME
+----
+gitnamespaces - Git namespaces
+
+DESCRIPTION
+-----------
+
+Git supports dividing the refs of a single repository into multiple
+namespaces, each of which has its own branches, tags, and HEAD.  Git can
+expose each namespace as an independent repository to pull from and push
+to, while sharing the object store, and exposing all the refs to
+operations such as linkgit:git-gc[1].
+
+Storing multiple repositories as namespaces of a single repository
+avoids storing duplicate copies of the same objects, such as when
+storing multiple branches of the same source.  The alternates mechanism
+provides similar support for avoiding duplicates, but alternates do not
+prevent duplication between new objects added to the repositories
+without ongoing maintenance, while namespaces do.
+
+To specify a namespace, set the `GIT_NAMESPACE` environment variable to
+the namespace.  For each ref namespace, git stores the corresponding
+refs in a directory under `refs/namespaces/`.  For example,
+`GIT_NAMESPACE=foo` will store refs under `refs/namespaces/foo/`.  You
+can also specify namespaces via the `--namespace` option to
+linkgit:git[1].
+
+Note that namespaces which include a `/` will expand to a hierarchy of
+namespaces; for example, `GIT_NAMESPACE=foo/bar` will store refs under
+`refs/namespaces/foo/refs/namespaces/bar/`.  This makes paths in
+`GIT_NAMESPACE` behave hierarchically, so that cloning with
+`GIT_NAMESPACE=foo/bar` produces the same result as cloning with
+`GIT_NAMESPACE=foo` and cloning from that repo with `GIT_NAMESPACE=bar`.  It
+also avoids ambiguity with strange namespace paths such as `foo/refs/heads/`,
+which could otherwise generate directory/file conflicts within the `refs`
+directory.
+
+linkgit:git-upload-pack[1] and linkgit:git-receive-pack[1] rewrite the
+names of refs as specified by `GIT_NAMESPACE`.  git-upload-pack and
+git-receive-pack will ignore all references outside the specified
+namespace.
+
+The smart HTTP server, linkgit:git-http-backend[1], will pass
+GIT_NAMESPACE through to the backend programs; see
+linkgit:git-http-backend[1] for sample configuration to expose
+repository namespaces as repositories.
+
+For a simple local test, you can use linkgit:git-remote-ext[1]:
+
+----------
+git clone ext::'git --namespace=foo %s /tmp/prefixed.git'
+----------
+
+SECURITY
+--------
+
+Anyone with access to any namespace within a repository can potentially
+access objects from any other namespace stored in the same repository.
+You can't directly say "give me object ABCD" if you don't have a ref to
+it, but you can do some other sneaky things like:
+
+. Claiming to push ABCD, at which point the server will optimize out the
+  need for you to actually send it. Now you have a ref to ABCD and can
+  fetch it (claiming not to have it, of course).
+
+. Requesting other refs, claiming that you have ABCD, at which point the
+  server may generate deltas against ABCD.
+
+None of this causes a problem if you only host public repositories, or
+if everyone who may read one namespace may also read everything in every
+other namespace (for instance, if everyone in an organization has read
+permission to every repository).

builtin/receive-pack.c

@@ -120,9 +120,25 @@ static int show_ref(const char *path, const unsigned char *sha1, int flag, void
 	return 0;
 }
 
+static int show_ref_cb(const char *path, const unsigned char *sha1, int flag, void *cb_data)
+{
+	path = strip_namespace(path);
+	/*
+	 * Advertise refs outside our current namespace as ".have"
+	 * refs, so that the client can use them to minimize data
+	 * transfer but will otherwise ignore them. This happens to
+	 * cover ".have" that are thrown in by add_one_alternate_ref()
+	 * to mark histories that are complete in our alternates as
+	 * well.
+	 */
+	if (!path)
+		path = ".have";
+	return show_ref(path, sha1, flag, cb_data);
+}
+
 static void write_head_info(void)
 {
-	for_each_ref(show_ref, NULL);
+	for_each_ref(show_ref_cb, NULL);
 	if (!sent_capabilities)
 		show_ref("capabilities^{}", null_sha1, 0, NULL);
 
@@ -333,6 +349,8 @@ static void refuse_unconfigured_deny_delete_current(void)
 static const char *update(struct command *cmd)
 {
 	const char *name = cmd->ref_name;
+	struct strbuf namespaced_name_buf = STRBUF_INIT;
+	const char *namespaced_name;
 	unsigned char *old_sha1 = cmd->old_sha1;
 	unsigned char *new_sha1 = cmd->new_sha1;
 	struct ref_lock *lock;
@@ -343,7 +361,10 @@ static const char *update(struct command *cmd)
 		return "funny refname";
 	}
 
-	if (is_ref_checked_out(name)) {
+	strbuf_addf(&namespaced_name_buf, "%s%s", get_git_namespace(), name);
+	namespaced_name = strbuf_detach(&namespaced_name_buf, NULL);
+
+	if (is_ref_checked_out(namespaced_name)) {
 		switch (deny_current_branch) {
 		case DENY_IGNORE:
 			break;
@@ -371,7 +392,7 @@ static const char *update(struct command *cmd)
 			return "deletion prohibited";
 		}
 
-		if (!strcmp(name, head_name)) {
+		if (!strcmp(namespaced_name, head_name)) {
 			switch (deny_delete_current) {
 			case DENY_IGNORE:
 				break;
@@ -427,14 +448,14 @@ static const char *update(struct command *cmd)
 			rp_warning("Allowing deletion of corrupt ref.");
 			old_sha1 = NULL;
 		}
-		if (delete_ref(name, old_sha1, 0)) {
+		if (delete_ref(namespaced_name, old_sha1, 0)) {
 			rp_error("failed to delete %s", name);
 			return "failed to delete";
 		}
 		return NULL; /* good */
 	}
 	else {
-		lock = lock_any_ref_for_update(name, old_sha1, 0);
+		lock = lock_any_ref_for_update(namespaced_name, old_sha1, 0);
 		if (!lock) {
 			rp_error("failed to lock %s", name);
 			return "failed to lock";
@@ -491,17 +512,29 @@ static void run_update_post_hook(struct command *commands)
 
 static void check_aliased_update(struct command *cmd, struct string_list *list)
 {
+	struct strbuf buf = STRBUF_INIT;
+	const char *dst_name;
 	struct string_list_item *item;
 	struct command *dst_cmd;
 	unsigned char sha1[20];
 	char cmd_oldh[41], cmd_newh[41], dst_oldh[41], dst_newh[41];
 	int flag;
 
-	const char *dst_name = resolve_ref(cmd->ref_name, sha1, 0, &flag);
+	strbuf_addf(&buf, "%s%s", get_git_namespace(), cmd->ref_name);
+	dst_name = resolve_ref(buf.buf, sha1, 0, &flag);
+	strbuf_release(&buf);
 
 	if (!(flag & REF_ISSYMREF))
 		return;
 
+	dst_name = strip_namespace(dst_name);
+	if (!dst_name) {
+		rp_error("refusing update to broken symref '%s'", cmd->ref_name);
+		cmd->skip_update = 1;
+		cmd->error_string = "broken symref";
+		return;
+	}
+
 	if ((item = string_list_lookup(list, dst_name)) == NULL)
 		return;
 

cache.h

@@ -394,6 +394,7 @@ static inline enum object_type object_type(unsigned int mode)
 }
 
 #define GIT_DIR_ENVIRONMENT "GIT_DIR"
+#define GIT_NAMESPACE_ENVIRONMENT "GIT_NAMESPACE"
 #define GIT_WORK_TREE_ENVIRONMENT "GIT_WORK_TREE"
 #define DEFAULT_GIT_DIR_ENVIRONMENT ".git"
 #define DB_ENVIRONMENT "GIT_OBJECT_DIRECTORY"
@@ -434,6 +435,8 @@ extern char *get_object_directory(void);
 extern char *get_index_file(void);
 extern char *get_graft_file(void);
 extern int set_git_dir(const char *path);
+extern const char *get_git_namespace(void);
+extern const char *strip_namespace(const char *namespaced_ref);
 extern const char *get_git_work_tree(void);
 extern const char *read_gitfile_gently(const char *path);
 extern void set_git_work_tree(const char *tree);

contrib/completion/git-completion.bash

@@ -1469,7 +1469,7 @@ _git_help ()
 	__gitcomp "$__git_all_commands $(__git_aliases)
 		attributes cli core-tutorial cvs-migration
 		diffcore gitk glossary hooks ignore modules
-		repository-layout tutorial tutorial-2
+		namespaces repository-layout tutorial tutorial-2
 		workflows
 		"
 }
@@ -2640,6 +2640,7 @@ _git ()
 			--exec-path
 			--html-path
 			--work-tree=
+			--namespace=
 			--help
 			"
 			;;

environment.c

@@ -8,6 +8,7 @@
  * are.
  */
 #include "cache.h"
+#include "refs.h"
 
 char git_default_email[MAX_GITNAME];
 char git_default_name[MAX_GITNAME];
@@ -66,6 +67,9 @@ int core_preload_index = 0;
 char *git_work_tree_cfg;
 static char *work_tree;
 
+static const char *namespace;
+static size_t namespace_len;
+
 static const char *git_dir;
 static char *git_object_dir, *git_index_file, *git_graft_file;
 
@@ -87,6 +91,27 @@ const char * const local_repo_env[LOCAL_REPO_ENV_SIZE + 1] = {
 	NULL
 };
 
+static char *expand_namespace(const char *raw_namespace)
+{
+	struct strbuf buf = STRBUF_INIT;
+	struct strbuf **components, **c;
+
+	if (!raw_namespace || !*raw_namespace)
+		return xstrdup("");
+
+	strbuf_addstr(&buf, raw_namespace);
+	components = strbuf_split(&buf, '/');
+	strbuf_reset(&buf);
+	for (c = components; *c; c++)
+		if (strcmp((*c)->buf, "/") != 0)
+			strbuf_addf(&buf, "refs/namespaces/%s", (*c)->buf);
+	strbuf_list_free(components);
+	if (check_ref_format(buf.buf) != CHECK_REF_FORMAT_OK)
+		die("bad git namespace path \"%s\"", raw_namespace);
+	strbuf_addch(&buf, '/');
+	return strbuf_detach(&buf, NULL);
+}
+
 static void setup_git_env(void)
 {
 	git_dir = getenv(GIT_DIR_ENVIRONMENT);
@@ -112,6 +137,8 @@ static void setup_git_env(void)
 		git_graft_file = git_pathdup("info/grafts");
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		read_replace_refs = 0;
+	namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
+	namespace_len = strlen(namespace);
 }
 
 int is_bare_repository(void)
@@ -132,6 +159,20 @@ const char *get_git_dir(void)
 	return git_dir;
 }
 
+const char *get_git_namespace(void)
+{
+	if (!namespace)
+		setup_git_env();
+	return namespace;
+}
+
+const char *strip_namespace(const char *namespaced_ref)
+{
+	if (prefixcmp(namespaced_ref, get_git_namespace()) != 0)
+		return NULL;
+	return namespaced_ref + namespace_len;
+}
+
 static int git_work_tree_initialized;
 
 /*