update: enable copy tracing for backwards and non-linear updates

As a followup to the issue4028 series, this fixes a variant of the issue
that can occur when updating with uncommited local changes.

The duplicated .hgsub warning is coming from wc.dirty(). We would previously
skip this call because it's only relevant when we're going to perform copy
tracing, which we didn't do before.

The change to the update summary line is because we now treat the rename as a
proper rename (which counts as a change), rather than an add+delete pair
(which counts as a change and a delete).

mercurial/merge.py

@@ -1555,15 +1555,16 b' def update(repo, node, branchmerge, forc'
                     pas = [p1]
 
         # deprecated config: merge.followcopies
-        followcopies = False
+        followcopies = repo.ui.configbool('merge', 'followcopies', True)
         if overwrite:
             pas = [wc]
+            followcopies = False
         elif pas == [p2]: # backwards
-            pas = [wc.p1()]
-        elif not branchmerge and not wc.dirty(missing=True):
-            pass
-        elif pas[0] and repo.ui.configbool('merge', 'followcopies', True):
-            followcopies = True
+            pas = [p1]
+        elif not pas[0]:
+            followcopies = False
+        if not branchmerge and not wc.dirty(missing=True):
+            followcopies = False
 
         ### calculate phase
         actionbyfile, diverge, renamedelete = calculateupdates(

tests/test-merge-local.t

@@ -66,7 +66,7 b' Local merge with bad merge tool:'
   merging zzz1_merge_ok
   merging zzz2_merge_bad
   warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
-  2 files updated, 1 files merged, 3 files removed, 1 files unresolved
+  2 files updated, 1 files merged, 2 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges
   [1]
 
@@ -104,7 +104,7 b' Local merge with conflicts:'
   merging zzz1_merge_ok
   merging zzz2_merge_bad
   warning: conflicts while merging zzz2_merge_bad! (edit, then use 'hg resolve --mark')
-  2 files updated, 1 files merged, 3 files removed, 1 files unresolved
+  2 files updated, 1 files merged, 2 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges
   [1]
 

tests/test-mq-subrepo.t

@@ -304,6 +304,7 b' handle subrepos safely on qrecord'
   record this change to '.hgsub'? [Ynesfdaq?] y
   
   warning: subrepo spec file '.hgsub' not found
+  warning: subrepo spec file '.hgsub' not found
   abort: uncommitted changes in subrepository 'sub'
   [255]
   % update substate when adding .hgsub w/clean updated subrepo
@@ -319,6 +320,7 b' handle subrepos safely on qrecord'
   record this change to '.hgsub'? [Ynesfdaq?] y
   
   warning: subrepo spec file '.hgsub' not found
+  warning: subrepo spec file '.hgsub' not found
   path sub
    source   sub
    revision b2fdb12cd82b021c3b7053d67802e77b6eeaee31

tests/test-up-local-change.t

@@ -67,6 +67,10 b''
   summary:     2
   
   $ hg --debug up 0
+  starting 4 threads for background file closing (?)
+    searching for copies back to rev 0
+    unmatched files in local (from topological common ancestor):
+     b
   resolving manifests
    branchmerge: False, force: False, partial: False
    ancestor: 1e71731e6fbb, local: 1e71731e6fbb+, remote: c19d34741b0a
@@ -222,4 +226,20 b' test a local add'
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg st
 
+test updating backwards through a rename
+
+  $ hg mv a b
+  $ hg ci -m b
+  $ echo b > b
+  $ hg up -q 0
+  $ hg st
+  M a
+  $ hg diff --nodates
+  diff -r cb9a9f314b8b a
+  --- a/a
+  +++ b/a
+  @@ -1,1 +1,1 @@
+  -a
+  +b
+
   $ cd ..