man/ostree: Document --repo option a bit more

This new information is already mostly part of `ostree.repo(5)`, though
let's put it in `ostree(1)` as well since that's where the switch is
officially documented.

Closes: #1560
Approved by: cgwalters

man/ostree.xml

@@ -111,14 +111,14 @@ Boston, MA 02111-1307, USA.
                 <term><option>--repo</option></term>
 
                 <listitem><para>
-                    For most commands,
-                    when run as non-root, repository is
-                    required.  If
-                    <command>ostree</command> is run as
-                    root, it is assumed operations will be
-                    performed on the
-                    <filename>/sysroot/ostree/repo</filename>
-                    repository.
+                    For most commands, a repository is
+                    required.  If unspecified, the current
+                    directory is used if it appears to be an
+                    OSTree repository. If it isn't, either
+                    the <envar>OSTREE_REPO</envar>
+                    environment variable is used, or the
+                    system repository located at
+                    <filename>/sysroot/ostree/repo</filename>.
                 </para></listitem>
             </varlistentry>
 

src/ostree/ot-main.c

@@ -46,7 +46,7 @@ static GOptionEntry global_entries[] = {
 };
 
 static GOptionEntry repo_entry[] = {
-  { "repo", 0, 0, G_OPTION_ARG_FILENAME, &opt_repo, "Path to OSTree repository (defaults to /sysroot/ostree/repo)", "PATH" },
+  { "repo", 0, 0, G_OPTION_ARG_FILENAME, &opt_repo, "Path to OSTree repository (defaults to current directory or /sysroot/ostree/repo)", "PATH" },
   { NULL }
 };