contrib/compress: proper lock handling

Lock the src repo before beginning the compression and lock the destination
repo before copying the revlogs.
Proper handling of exceptions.

contrib/compress.py

@@ -1,54 +1,67 b''
 # Copyright 2010 Pradeepkumar Gayam <[e-mail]>
 #
 # Author(s):
 # Pradeepkumar Gayam <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 
 from mercurial import hg, changegroup, localrepo
+from mercurial.lock import release
+import weakref
 
 def compress(ui, repo, dest):
     dest = hg.localpath(ui.expandpath(dest))
     target = localrepo.instance(ui, dest, create=True)
+
+    tr = lock = tlock = None
+    try:
+        lock = repo.lock()
+        tlock = target.lock()
     tr = target.transaction("compress")
+        trp = weakref.proxy(tr)
+
     src_cl = repo.changelog
     tar_cl = target.changelog
     changedfiles = set()
     mmfs = {}
     collect = changegroup.collector(src_cl, mmfs, changedfiles)
     total = len(repo)
 
     for r in src_cl:
         p = [src_cl.node(i) for i in src_cl.parentrevs(r)]
-        nd = tar_cl.addrevision(src_cl.revision(src_cl.node(r)), tr,
+            nd = tar_cl.addrevision(src_cl.revision(src_cl.node(r)), trp,
                                  src_cl.linkrev(r), p[0], p[1])
         collect(nd)
         ui.progress(('adding changesets'), r, unit=('revisions'),
                     total=total)
 
     src_mnfst = repo.manifest
     tar_mnfst = target.manifest
     for r in src_mnfst:
         p = [src_mnfst.node(i) for i in src_mnfst.parentrevs(r)]
-        tar_mnfst.addrevision(src_mnfst.revision(src_mnfst.node(r)), tr,
+            tar_mnfst.addrevision(src_mnfst.revision(src_mnfst.node(r)), trp,
                                src_mnfst.linkrev(r), p[0], p[1])
         ui.progress(('adding manifest'), r, unit=('revisions'),
                     total=total)
 
     total = len(changedfiles)
     for cnt, f in enumerate(changedfiles):
         sf = repo.file(f)
         tf = target.file(f)
         for r in sf:
             p = [sf.node(i) for i in sf.parentrevs(r)]
-            tf.addrevision(sf.revision(sf.node(r)), tr, sf.linkrev(r),
+                tf.addrevision(sf.revision(sf.node(r)), trp, sf.linkrev(r),
                                p[0], p[1])
-        ui.progress(('adding files'), cnt, item=f, unit=('file'), total=total)
-
+            ui.progress(('adding files'), cnt, item=f, unit=('file'),
+                        total=total)
     tr.close()
+    finally:
+        if tr:
+            tr.release()
+        release(tlock, lock)
 
 cmdtable = {
     "compress" : (compress, [], "DEST")
     }