strip: simplify some repeated conditions

We check "if saveheads or savebases" in several places to see if we
should or have created a bundle of the changesets to apply after
truncating the revlogs. One of the conditions is actually just "if
saveheads", but since there can't be savebases without saveheads, that
is effectively the same condition. It seems simpler to check only once
and from then on see if we created the file.

mercurial/repair.py

@@ -147,7 +147,8 def strip(ui, repo, nodelist, backup=Tru
                        vfs.join(backupfile))
         repo.ui.log("backupbundle", "saved backup bundle to %s\n",
                     vfs.join(backupfile))
-    if saveheads or savebases:
+    chgrpfile = None
+    if saveheads:
         # do not compress partial bundle if we remove it from disk later
         chgrpfile = _bundle(repo, savebases, saveheads, node, 'temp',
                             compress=False)
@@ -184,7 +185,7 def strip(ui, repo, nodelist, backup=Tru
                 if troffset == 0:
                     repo.store.markremoved(file)
 
-        if saveheads or savebases:
+        if chgrpfile:
             ui.note(_("adding branch\n"))
             f = vfs.open(chgrpfile, "rb")
             gen = exchange.readbundle(ui, f, chgrpfile, vfs)
@@ -229,12 +230,12 def strip(ui, repo, nodelist, backup=Tru
         if backupfile:
             ui.warn(_("strip failed, full bundle stored in '%s'\n")
                     % vfs.join(backupfile))
-        elif saveheads:
+        elif chgrpfile:
             ui.warn(_("strip failed, partial bundle stored in '%s'\n")
                     % vfs.join(chgrpfile))
         raise
     else:
-        if saveheads or savebases:
+        if chgrpfile:
             # Remove partial backup only if there were no exceptions
             vfs.unlink(chgrpfile)