pull: Support specifying exact commit to pull via branch@commit

I don't know why we didn't do this a long time ago.  This extends the
pull API to allow grabbing a specific commit, and will set the branch
to it.  There's some support for this in the deploy engine, but there
are a lot of reasons to support it for raw pulls (such as subset
mirroring cases).

In fact I'm thinking we should also have the override-version logic
here too.

NOTE: One thing I debated here is inventing a new syntax on the
command line.  Git doesn't seem to have this functionality (probably
because it'd be rarely used). The '@' character at least doesn't
conflict with anything.

Anyways, I wanted this for some other test cases.  Without this,
writing tests that go between different commits is more awkward as one
must generate the content in one repo, then pull downstream, then
generate more content, then pull again.  But now I can just keep track
of commit IDs and do exactly what I want without synchronizing the
tests.

man/ostree-pull.xml

@@ -111,14 +111,37 @@ Boston, MA 02111-1307, USA.
         <title>Description</title>
 
         <para>
-            Downloads all content corresponding to the provided branch or commit from the given remote.
+	  This command can retrieve just a specific commit, or go all
+	  the way to performing a full mirror of the remote
+	  repository.  If no <literal>BRANCH</literal> is specified,
+	  all branches are retrieved.
         </para>
+
+	<para>
+	  A special syntax in the <literal>@</literal> character allows
+	  specifying a specific commit to retrieve from a branch.  This
+	</para>
+
     </refsect1>
 
     <refsect1>
         <title>Example</title>
 
-        <para><command>$ ostree pull remote_name</command></para>
+        <para><command>$ ostree --repo=repo pull --depth=-1 --mirror remote_name</command></para>
+
+	<para>Perform a complete mirror of the remote.  (This is
+	likely most useful if your repository is also
+	<literal>archive-z2</literal> mode)</para>
+
+        <para><command>$ ostree --repo=repo pull remote_name exampleos/x86_64/standard</command></para>
+
+	<para>Fetch the most recent commit to <literal>exampleos/x86_64/standard</literal>.</para>
+
+        <para><command>$ ostree --repo=repo pull remote_name exampleos/x86_64/standard@98ea6e4f216f2fb4b69fff9b3a44842c38686ca685f3f55dc48c5d3fb1107be4</command></para>
+
+	<para>Download the specific commit starting with
+	<literal>98ea6e</literal> as if it was the latest commit for
+	<literal>exampleos/x86_64/standard</literal>.</para>
     </refsect1>
 
 </refentry>

src/libostree/ostree-repo-pull.c

@@ -1762,6 +1762,7 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
   OstreeRepoPullFlags flags = 0;
   const char *dir_to_pull = NULL;
   char **refs_to_fetch = NULL;
+  char **override_commit_ids = NULL;
   GSource *update_timeout = NULL;
   gboolean disable_static_deltas = FALSE;
 
@@ -1776,9 +1777,12 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
       (void) g_variant_lookup (options, "override-remote-name", "s", &pull_data->remote_name);
       (void) g_variant_lookup (options, "depth", "i", &pull_data->maxdepth);
       (void) g_variant_lookup (options, "disable-static-deltas", "b", &disable_static_deltas);
+      (void) g_variant_lookup (options, "override-commit-ids", "^a&s", &override_commit_ids);
     }
 
   g_return_val_if_fail (pull_data->maxdepth >= -1, FALSE);
+  if (refs_to_fetch && override_commit_ids)
+    g_return_val_if_fail (g_strv_length (refs_to_fetch) == g_strv_length (override_commit_ids), FALSE);
 
   if (dir_to_pull)
     g_return_val_if_fail (dir_to_pull[0] == '/', FALSE);
@@ -2069,8 +2073,10 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
     } 
   else if (refs_to_fetch != NULL)
     {
-      char **strviter;
+      char **strviter = refs_to_fetch;
-      for (strviter = refs_to_fetch; *strviter; strviter++)
+      char **commitid_strviter = override_commit_ids ? override_commit_ids : NULL;
+
+      while (*strviter)
         {
           const char *branch = *strviter;
 
@@ -2081,8 +2087,13 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
             }
           else
             {
-              g_hash_table_insert (requested_refs_to_fetch, g_strdup (branch), NULL);
+              char *commitid = commitid_strviter ? g_strdup (*commitid_strviter) : NULL;
+              g_hash_table_insert (requested_refs_to_fetch, g_strdup (branch), commitid);
             }
+          
+          strviter++;
+          if (commitid_strviter)
+            commitid_strviter++;
         }
     }
   else
@@ -2109,8 +2120,16 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
   while (g_hash_table_iter_next (&hash_iter, &key, &value))
     {
       const char *branch = key;
+      const char *override_commitid = value;
       char *contents = NULL;
 
+      /* Support specifying "" for an override commitid */
+      if (override_commitid && *override_commitid)
+        {
+          g_hash_table_replace (requested_refs_to_fetch, g_strdup (branch), g_strdup (override_commitid));
+        }
+      else    
+        {
           if (pull_data->summary)
             {
               gsize commit_size = 0;
@@ -2128,10 +2147,10 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
               if (!fetch_ref_contents (pull_data, branch, &contents, cancellable, error))
                 goto out;
             }
-      
           /* Transfer ownership of contents */
           g_hash_table_replace (requested_refs_to_fetch, g_strdup (branch), contents);
         }
+    }
 
   /* Create the state directory here - it's new with the commitpartial code,
    * and may not exist in older repositories.

src/libostree/ostree-repo.c

@@ -3784,6 +3784,7 @@ ostree_repo_pull_one_dir (OstreeRepo               *self,
  *   * flags (i): An instance of #OstreeRepoPullFlags
  *   * refs: (as): Array of string refs
  *   * depth: (i): How far in the history to traverse; default is 0, -1 means infinite
+ *   * override-commit-ids: (as): Array of specific commit IDs to fetch for refs
  */
 gboolean
 ostree_repo_pull_with_options (OstreeRepo             *self,

src/ostree/ot-builtin-pull.c

@@ -70,6 +70,7 @@ ostree_builtin_pull (int argc, char **argv, GCancellable *cancellable, GError **
   OstreeRepoPullFlags pullflags = 0;
   GSConsole *console = NULL;
   g_autoptr(GPtrArray) refs_to_fetch = NULL;
+  g_autoptr(GPtrArray) override_commit_ids = NULL;
   glnx_unref_object OstreeAsyncProgress *progress = NULL;
   gulong signal_handler_id = 0;
 
@@ -102,9 +103,36 @@ ostree_builtin_pull (int argc, char **argv, GCancellable *cancellable, GError **
       if (argc > 2)
         {
           int i;
-          refs_to_fetch = g_ptr_array_new ();
+          refs_to_fetch = g_ptr_array_new_with_free_func (g_free);
+
           for (i = 2; i < argc; i++)
-            g_ptr_array_add (refs_to_fetch, argv[i]);
+            {
+              const char *at = strrchr (argv[i], '@');
+
+              if (at)
+                {
+                  guint j;
+                  const char *override_commit_id = at + 1;
+
+                  if (!ostree_validate_checksum_string (override_commit_id, error))
+                    goto out;
+
+                  if (!override_commit_ids)
+                    override_commit_ids = g_ptr_array_new_with_free_func (g_free);
+
+                  /* Backfill */
+                  for (j = 2; j < i; i++)
+                    g_ptr_array_add (override_commit_ids, g_strdup (""));
+
+                  g_ptr_array_add (override_commit_ids, g_strdup (override_commit_id));
+                  g_ptr_array_add (refs_to_fetch, g_strndup (argv[i], at - argv[i]));
+                }
+              else
+                {
+                  g_ptr_array_add (refs_to_fetch, g_strdup (argv[i]));
+                }
+            }
+
           g_ptr_array_add (refs_to_fetch, NULL);
         }
     }
@@ -147,6 +175,10 @@ ostree_builtin_pull (int argc, char **argv, GCancellable *cancellable, GError **
     g_variant_builder_add (&builder, "{s@v}", "disable-static-deltas",
                            g_variant_new_variant (g_variant_new_boolean (opt_disable_static_deltas)));
 
+    if (override_commit_ids)
+      g_variant_builder_add (&builder, "{s@v}", "override-commit-ids",
+                             g_variant_new_variant (g_variant_new_strv ((const char*const*)override_commit_ids->pdata, override_commit_ids->len)));
+
     if (!ostree_repo_pull_with_options (repo, remote, g_variant_builder_end (&builder),
                                         progress, cancellable, error))
       goto out;

tests/pull-test.sh

@@ -72,6 +72,21 @@ $OSTREE show --print-detached-metadata-key=SIGNATURE main > main-meta
 assert_file_has_content main-meta "HANCOCK"
 echo "ok pull detached metadata"
 
+cd ${test_tmpdir}
+mkdir parentpullrepo
+${CMD_PREFIX} ostree --repo=parentpullrepo init --mode=archive-z2
+${CMD_PREFIX} ostree --repo=parentpullrepo remote add --set=gpg-verify=false origin file://$(pwd)/ostree-srv/gnomerepo
+parent_rev=$(ostree --repo=ostree-srv/gnomerepo rev-parse main^)
+rev=$(ostree --repo=ostree-srv/gnomerepo rev-parse main)
+${CMD_PREFIX} ostree --repo=parentpullrepo pull origin main@${parent_rev}
+${CMD_PREFIX} ostree --repo=parentpullrepo rev-parse origin:main > main.txt
+assert_file_has_content main.txt ${parent_rev}
+${CMD_PREFIX} ostree --repo=parentpullrepo fsck
+${CMD_PREFIX} ostree --repo=parentpullrepo pull origin main
+${CMD_PREFIX} ostree --repo=parentpullrepo rev-parse origin:main > main.txt
+assert_file_has_content main.txt ${rev}
+echo "ok pull specific commit"
+
 cd ${test_tmpdir}
 repo_init
 ${CMD_PREFIX} ostree --repo=repo pull origin main