revert: ensure that copies and renames are honored (issue3920)

Previously, we restored the states of files, but not the additional
information the dirstate uses to track copies and renames.

mercurial/cmdutil.py

@@ -2055,6 +2055,12 b' def revert(ui, repo, ctx, parents, *pats'
                 checkout(f)
                 normal(f)
 
+            copied = copies.pathcopies(repo[parent], ctx)
+
+            for f in add[0] + undelete[0] + revert[0]:
+                if f in copied:
+                    repo.dirstate.copy(copied[f], f)
+
             if targetsubs:
                 # Revert the subrepos on the revert list
                 for sub in targetsubs:

tests/test-revert.t

@@ -275,4 +275,28 b' should silently revert the named files'
   $ hg revert --no-backup ignored removed
   $ hg st -mardi
 
+someone set up us the copies
+
+  $ rm .hgignore
+  $ hg update -C
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg mv ignored allyour
+  $ hg copy removed base
+  $ hg commit -m rename
+
+copies and renames, you have no chance to survive make your time (issue3920)
+
+  $ hg update '.^'
+  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
+  $ hg revert -rtip -a
+  adding allyour
+  adding base
+  removing ignored
+  $ hg status -C
+  A allyour
+    ignored
+  A base
+    removed
+  R ignored
+
   $ cd ..