pull: better description for --mirror

Describe the behaviour of --mirror a bit better.

Closes: #1100

Closes: #1099
Approved by: dustymabe

src/libostree/ostree-repo.h

@@ -1081,7 +1081,7 @@ gboolean ostree_repo_prune_from_reachable (OstreeRepo             *self,
 /**
  * OstreeRepoPullFlags:
  * @OSTREE_REPO_PULL_FLAGS_NONE: No special options for pull
- * @OSTREE_REPO_PULL_FLAGS_MIRROR: Write out refs suitable for mirrors
+ * @OSTREE_REPO_PULL_FLAGS_MIRROR: Write out refs suitable for mirrors and fetch all refs if none requested
  * @OSTREE_REPO_PULL_FLAGS_COMMIT_ONLY: Fetch only the commit metadata
  * @OSTREE_REPO_PULL_FLAGS_UNTRUSTED: Don't trust local remote
  * @OSTREE_REPO_PULL_FLAGS_BAREUSERONLY_FILES: Since 2017.7.  Reject writes of content objects with modes outside of 0775.

src/ostree/ot-builtin-pull.c

@@ -55,7 +55,7 @@ static GOptionEntry options[] = {
    { "disable-fsync", 0, 0, G_OPTION_ARG_NONE, &opt_disable_fsync, "Do not invoke fsync()", NULL },
    { "disable-static-deltas", 0, 0, G_OPTION_ARG_NONE, &opt_disable_static_deltas, "Do not use static deltas", NULL },
    { "require-static-deltas", 0, 0, G_OPTION_ARG_NONE, &opt_require_static_deltas, "Require static deltas", NULL },
-   { "mirror", 0, 0, G_OPTION_ARG_NONE, &opt_mirror, "Write refs suitable for a mirror", NULL },
+   { "mirror", 0, 0, G_OPTION_ARG_NONE, &opt_mirror, "Write refs suitable for a mirror and fetches all refs if none provided", NULL },
    { "subpath", 0, 0, G_OPTION_ARG_FILENAME_ARRAY, &opt_subpaths, "Only pull the provided subpath(s)", NULL },
    { "untrusted", 0, 0, G_OPTION_ARG_NONE, &opt_untrusted, "Do not trust (local) sources", NULL },
    { "bareuseronly-files", 0, 0, G_OPTION_ARG_NONE, &opt_bareuseronly_files, "Reject regular files with mode outside of 0775 (world writable, suid, etc.)", NULL },