update: don't overwrite untracked ignored files on update

When looking for untracked files that would conflict with a tracked
file in the target revision (or the remote side of a merge), we
explcitly exclude ignored files. The code was added in 7e30f5f2285f
(merge: refactor unknown file conflict checking, 2012-02-09), but it
seems like only unknown, not ignored, files were considered since the
beginning of time.

Although ignored files are mostly build outputs and backup files, we
should still not overwrite them. Fix by simply removing the explicit
check.

mercurial/merge.py

@@ -298,8 +298,7 b' class mergestate(object):'
         return r
 
 def _checkunknownfile(repo, wctx, mctx, f):
-    return (not repo.dirstate._ignore(f)
-        and os.path.isfile(repo.wjoin(f))
+    return (os.path.isfile(repo.wjoin(f))
         and repo.wopener.audit.check(f)
         and repo.dirstate.normalize(f) not in repo.dirstate
         and mctx[f].cmp(wctx[f]))

tests/test-up-local-change.t

@@ -231,8 +231,6 b' test conflicting untracked files'
 
 test conflicting untracked ignored file
 
-BROKEN: the ignored file gets overwritten by the remote version
-
   $ hg up -qC 0
   $ echo ignored > .hgignore
   $ hg add .hgignore
@@ -246,9 +244,9 b' BROKEN: the ignored file gets overwritte'
   $ echo untracked > ignored
   $ hg st
   $ hg up 'desc("add ignored file")'
-  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
-  $ cat ignored
-  ignored
+  ignored: untracked file differs
+  abort: untracked files in working directory differ from files in requested revision
+  [255]
 
 test a local add