Issue919: add a standard extension to recreate hardlinks between repositories.

Having to run a standalone Python script from the contrib dir is a nuisance.
Also makes various improvements to locking, file discovery, etc.
Should also update: http://www.selenic.com/mercurial/wiki/index.cgi/RecreateHardlinksBetweenRepositories

hgext/relink.py

@@ -1,52 +1,74 b''
-#!/usr/bin/env python
+# Mercurial extension to provide 'hg relink' command
 #
 # Copyright (C) 2007 Brendan Cully <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2, incorporated herein by reference.
 
-import os, sys
+"""recreates hardlinks between repository clones"""
 
-class ConfigError(Exception): pass
+from mercurial import cmdutil, hg, util
+from mercurial.i18n import _
+import os, stat
+
+def relink(ui, repo, origin=None, **opts):
+    """recreate hardlinks between two repositories
 
-def usage():
-    print """relink <source> <destination>
-    Recreate hard links between source and destination repositories"""
+    When repositories are cloned locally, their data files will be hardlinked
+    so that they only use the space of a single repository.
+
+    Unfortunately, subsequent pulls into either repository will break hardlinks
+    for any files touched by the new changesets, even if both repositories end
+    up pulling the same changes.
+
+    Similarly, passing --rev to "hg clone" will fail to use
+    any hardlinks, falling back to a complete copy of the source repository.
+
+    This command lets you recreate those hardlinks and reclaim that wasted
+    space.
 
-class Config:
-    def __init__(self, args):
-        if len(args) != 3:
-            raise ConfigError("wrong number of arguments")
-        self.src = os.path.abspath(args[1])
-        self.dst = os.path.abspath(args[2])
-        for d in (self.src, self.dst):
-            if not os.path.exists(os.path.join(d, '.hg')):
-                raise ConfigError("%s: not a mercurial repository" % d)
+    This repository will be relinked to share space with ORIGIN, which must be
+    on the same local disk. If ORIGIN is omitted, looks for "default-relink",
+    then "default", in [paths].
 
-def collect(src):
+    Do not attempt any read operations on this repository while the command is
+    running. (Both repositories will be locked against writes.)
+    """
+    src = hg.repository(
+        cmdutil.remoteui(repo, opts),
+        ui.expandpath(origin or 'default-relink', origin or 'default'))
+    if not src.local():
+        raise util.Abort('must specify local origin repository')
+    ui.status(_('relinking %s to %s\n') % (src.store.path, repo.store.path))
+    locallock = repo.lock()
+    try:
+        remotelock = src.lock()
+        try:
+            candidates = collect(src.store.path, ui)
+            targets = prune(candidates, repo.store.path, ui)
+            do_relink(src.store.path, repo.store.path, targets, ui)
+        finally:
+            remotelock.release()
+    finally:
+        locallock.release()
+
+def collect(src, ui):
     seplen = len(os.path.sep)
     candidates = []
     for dirpath, dirnames, filenames in os.walk(src):
         relpath = dirpath[len(src) + seplen:]
         for filename in filenames:
-            if not filename.endswith('.i'):
+            if not filename[-2:] in ('.d', '.i'):
                 continue
             st = os.stat(os.path.join(dirpath, filename))
+            if not stat.S_ISREG(st.st_mode):
+                continue
             candidates.append((os.path.join(relpath, filename), st))
 
+    ui.status(_('collected %d candidate storage files\n') % len(candidates))
     return candidates
 
-def prune(candidates, dst):
-    def getdatafile(path):
-        if not path.endswith('.i'):
-            return None, None
-        df = path[:-1] + 'd'
-        try:
-            st = os.stat(df)
-        except OSError:
-            return None, None
-        return df, st
-
+def prune(candidates, dst, ui):
     def linkfilter(dst, st):
         try:
             ts = os.stat(dst)
@@ -57,9 +79,9 b' def prune(candidates, dst):'
             return False
         if st.st_dev != ts.st_dev:
             # No point in continuing
-            raise Exception('Source and destination are on different devices')
+            raise util.Abort(
+                _('source and destination are on different devices'))
         if st.st_size != ts.st_size:
-            # TODO: compare revlog heads
             return False
         return st
 
@@ -68,15 +90,14 b' def prune(candidates, dst):'
         tgt = os.path.join(dst, fn)
         ts = linkfilter(tgt, st)
         if not ts:
+            ui.debug(_('not linkable: %s\n') % fn)
             continue
         targets.append((fn, ts.st_size))
-        df, ts = getdatafile(tgt)
-        if df:
-            targets.append((fn[:-1] + 'd', ts.st_size))
 
+    ui.status(_('pruned down to %d probably relinkable files\n') % len(targets))
     return targets
 
-def relink(src, dst, files):
+def do_relink(src, dst, files, ui):
     def relinkfile(src, dst):
         bak = dst + '.bak'
         os.rename(dst, bak)
@@ -91,7 +112,10 b' def relink(src, dst, files):'
     relinked = 0
     savedbytes = 0
 
+    pos = 0
+    total = len(files)
     for f, sz in files:
+        pos += 1
         source = os.path.join(src, f)
         tgt = os.path.join(dst, f)
         sfp = file(source)
@@ -103,26 +127,23 b' def relink(src, dst, files):'
                 break
             sin = sfp.read(CHUNKLEN)
         if sin:
+            ui.debug(_('not linkable: %s\n') % f)
             continue
         try:
             relinkfile(source, tgt)
-            print 'Relinked %s' % f
+            ui.progress(_('relink'), pos, f, _(' files'), total)
             relinked += 1
             savedbytes += sz
         except OSError, inst:
-            print '%s: %s' % (tgt, str(inst))
+            ui.warn(_('%s: %s\n') % (tgt, str(inst)))
 
-    print 'Relinked %d files (%d bytes reclaimed)' % (relinked, savedbytes)
+    ui.status(_('relinked %d files (%d bytes reclaimed)\n') %
+              (relinked, savedbytes))
 
-try:
-    cfg = Config(sys.argv)
-except ConfigError, inst:
-    print str(inst)
-    usage()
-    sys.exit(1)
-
-src = os.path.join(cfg.src, '.hg')
-dst = os.path.join(cfg.dst, '.hg')
-candidates = collect(src)
-targets = prune(candidates, dst)
-relink(src, dst, targets)
+cmdtable = {
+    'relink': (
+        relink,
+        [],
+        _('[ORIGIN]')
+    )
+}