clone: fall back to pull if we can't lock the source repo

tests/test-pull-permission

@@ -0,0 +1,20 b''
+#!/bin/sh
+
+mkdir a
+cd a
+hg init
+echo foo > b
+hg add b
+hg ci -m "b" -d "0 0"
+
+chmod -w .hg
+
+cd ..
+
+hg clone a b
+cd b
+hg verify
+
+cd ..
+
+chmod +w a/.hg # let test clean up

tests/test-pull-permission.out

@@ -0,0 +1,10 b''
+requesting all changes
+adding changesets
+adding manifests
+adding file changes
+added 1 changesets with 1 changes to 1 files
+checking changesets
+checking manifests
+crosschecking files in changesets and manifests
+checking files
+1 files, 1 changesets, 1 total revisions

mercurial/commands.py

@@ -621,15 +621,23 b' def clone(ui, source, dest=None, **opts)'
     abspath = source
     other = hg.repository(ui, source)
 
+    copy = False
     if other.dev() != -1:
         abspath = os.path.abspath(source)
+        copy = True
 
-        # we use a lock here because if we race with commit, we can
-        # end up with extra data in the cloned revlogs that's not
-        # pointed to by changesets, thus causing verify to fail
-        l1 = lock.lock(os.path.join(source, ".hg", "lock"))
+    if copy:
+        try:
+            # we use a lock here because if we race with commit, we
+            # can end up with extra data in the cloned revlogs that's
+            # not pointed to by changesets, thus causing verify to
+            # fail
+            l1 = lock.lock(os.path.join(source, ".hg", "lock"))
+        except OSError:
+            copy = False
 
-        # and here to avoid premature writing to the target
+    if copy:
+        # we lock here to avoid premature writing to the target
         os.mkdir(os.path.join(dest, ".hg"))
         l2 = lock.lock(os.path.join(dest, ".hg", "lock"))