amend: check for file modifications when updating dirstate (issue6233)

Previously, we called dirstate.normal(f), which would put information into the
dirstate claiming that the file on disk is what it "should be" for the current
checkout, and it would have the size and timestamp of the most recent
modification to the file (which is not necessarily the one we just committed).
If the file was modified while the commit message editor was open, we would put
incorrect information into the dirstate.

Differential Revision: https://phab.mercurial-scm.org/D7521

mercurial/cmdutil.py

@@ -3054,11 +3054,13 b' def amend(ui, repo, old, extra, pats, op'
         # selectively update the dirstate only for the amended files.
         dirstate = repo.dirstate
 
-        # Update the state of the files which were added and
-        # and modified in the amend to "normal" in the dirstate.
+        # Update the state of the files which were added and modified in the
+        # amend to "normal" in the dirstate. We need to use "normallookup" since
+        # the files may have changed since the command started; using "normal"
+        # would mark them as clean but with uncommitted contents.
         normalfiles = set(wctx.modified() + wctx.added()) & filestoamend
         for f in normalfiles:
-            dirstate.normal(f)
+            dirstate.normallookup(f)
 
         # Update the state of files which were removed in the amend
         # to "removed" in the dirstate.

tests/test-amend.t

@@ -476,3 +476,33 b' hg used to include the changes to `a` an'
    a |  2 +-
    b |  2 +-
    2 files changed, 2 insertions(+), 2 deletions(-)
+
+Modifying a file while the editor is open can cause dirstate corruption
+(issue6233)
+
+  $ cd $TESTTMP
+  $ hg init modify-during-amend; cd modify-during-amend
+  $ echo r0 > foo; hg commit -qAm "r0"
+  $ echo alpha > foo; hg commit -qm "alpha"
+  $ echo beta >> foo
+  $ cat > $TESTTMP/sleepy_editor.sh <<EOF
+  > echo hi > "\$1"
+  > sleep 3
+  > EOF
+  $ HGEDITOR="sh $TESTTMP/sleepy_editor.sh" hg commit --amend &
+  $ sleep 1
+  $ echo delta >> foo
+  $ sleep 3
+  $ if (hg diff -c . | grep 'delta' >/dev/null) || [[ -n "$(hg status)" ]]; then
+  >   echo "OK."
+  > else
+  >   echo "Bug detected. 'delta' is not part of the commit OR the wdir"
+  >   echo "Diff and status before rebuild:"
+  >   hg diff
+  >   hg status
+  >   hg debugrebuilddirstate
+  >   echo "Diff and status after rebuild:"
+  >   hg diff
+  >   hg status
+  > fi
+  OK.