repo: Make repo/tmp expiry configurable via tmp-expiry-seconds

We were arbitrarily only deleting content after exactly one day.  Some
use cases may want something else; make it configurable.

Closes: #170
Approved by: jlebon

src/libostree/ostree-repo-commit.c

@@ -1349,11 +1349,12 @@ cleanup_tmpdir (OstreeRepo        *self,
           if (stbuf.st_mtime > curtime_secs)
             continue;
 
-          /* Now, we arbitrarily delete files/directories older than a
-           * day, since that's what we were doing before we had locking.
+          /* Now, we're pruning content based on the expiry, which
+           * defaults to a day.  That's what we were doing before we
+           * had locking...but in future we can be smarter here.
            */
           delta = curtime_secs - stbuf.st_mtime;
-          if (delta > 60*60*24)
+          if (delta > self->tmp_expiry_seconds)
             {
               if (!glnx_shutil_rm_rf_at (dfd_iter.fd, dent->d_name, cancellable, error))
                 goto out;

src/libostree/ostree-repo-private.h

@@ -98,6 +98,7 @@ struct OstreeRepo {
   OstreeRepoMode mode;
   gboolean enable_uncompressed_cache;
   gboolean generate_sizes;
+  guint64 tmp_expiry_seconds;
 
   OstreeRepo *parent_repo;
 };

src/libostree/ostree-repo.c

@@ -2561,6 +2561,16 @@ ostree_repo_open (OstreeRepo    *self,
       ostree_repo_set_disable_fsync (self, TRUE);
   }
 
+  { g_autofree char *tmp_expiry_seconds = NULL;
+
+    /* 86400 secs = one day */
+    if (!ot_keyfile_get_value_with_default (self->config, "core", "tmp-expiry-secs", "86400",
+                                            &tmp_expiry_seconds, error))
+      goto out;
+
+    self->tmp_expiry_seconds = g_ascii_strtoull (tmp_expiry_seconds, NULL, 10);
+  }
+
   if (!append_remotes_d (self, cancellable, error))
     goto out;