clone: for local clones, copy over filtered branchcaches as well (issue4286)

Local clones copy/hardlink over files directly, so the branchcaches should all
be valid. There's a slight chance that a read operation would update one of the
branchcaches, but we hold a lock over the source repo so they shouldn't cause
an invalid branchcache to be copied over, just a different, valid one.

mercurial/hg.py

@@ -11,7 +11,7 @@ from lock import release
 from node import hex, nullid
 import localrepo, bundlerepo, unionrepo, httppeer, sshpeer, statichttprepo
 import bookmarks, lock, util, extensions, error, node, scmutil, phases, url
-import cmdutil, discovery
+import cmdutil, discovery, repoview
 import merge as mergemod
 import verify as verifymod
 import errno, os, shutil
@@ -366,13 +366,20 @@ def clone(ui, peeropts, source, dest=None, pull=False, rev=None,
 
             # Recomputing branch cache might be slow on big repos,
             # so just copy it
+            def copybranchcache(fname):
+                srcbranchcache = srcrepo.join('cache/%s' % fname)
+                dstbranchcache = os.path.join(dstcachedir, fname)
+                if os.path.exists(srcbranchcache):
+                    if not os.path.exists(dstcachedir):
+                        os.mkdir(dstcachedir)
+                    util.copyfile(srcbranchcache, dstbranchcache)
+
             dstcachedir = os.path.join(destpath, 'cache')
-            srcbranchcache = srcrepo.join('cache/branch2')
-            dstbranchcache = os.path.join(dstcachedir, 'branch2')
-            if os.path.exists(srcbranchcache):
-                if not os.path.exists(dstcachedir):
-                    os.mkdir(dstcachedir)
-                util.copyfile(srcbranchcache, dstbranchcache)
+            # In local clones we're copying all nodes, not just served
+            # ones. Therefore copy all branchcaches over.
+            copybranchcache('branch2')
+            for cachename in repoview.filtertable:
+                copybranchcache('branch2-%s' % cachename)
 
             # we need to re-init the repo after manually copying the data
             # into it

tests/test-clone.t

@@ -25,12 +25,25 @@ List files in store/data (should show a 'b.d'):
   .hg/store/data/b.d
   .hg/store/data/b.i
 
+Trigger branchcache creation:
+
+  $ hg branches
+  default                       10:a7949464abda
+  $ ls .hg/cache
+  branch2-served
+
 Default operation:
 
   $ hg clone . ../b
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd ../b
+
+Ensure branchcache got copied over:
+
+  $ ls .hg/cache
+  branch2-served
+
   $ cat a
   a
   $ hg verify
@@ -58,6 +71,12 @@ No update, with debug option:
   listing keys for "bookmarks"
 #endif
   $ cd ../c
+
+Ensure branchcache got copied over:
+
+  $ ls .hg/cache
+  branch2-served
+
   $ cat a 2>/dev/null || echo "a not present"
   a not present
   $ hg verify