crecord: edit during hg crecord should preserve cursor position (issue5041)

This patch adds a variable to keep track of what hunk was selected
before the edit. We use that variable to select the hunk or its
replacement after the edit.

mercurial/crecord.py

@@ -1551,6 +1551,9 b' are you sure you want to review/edit and'
         if not isinstance(item, uihunk):
             return
 
+        # To go back to that hunk or its replacement at the end of the edit
+        itemindex = item.parentitem().hunks.index(item)
+
         beforeadded, beforeremoved = item.added, item.removed
         newpatches = editpatchwitheditor(self, item)
         if newpatches is None:
@@ -1575,6 +1578,8 b' are you sure you want to review/edit and'
         if self.emptypatch():
             header.hunks = hunksbefore + [item] + hunksafter
         self.currentselecteditem = header
+        if len(header.hunks) > itemindex:
+            self.currentselecteditem = header.hunks[itemindex]
 
         if not test:
             updateui(self)

tests/test-commit-interactive-curses.t

@@ -193,3 +193,33 b' Amend option works'
   +++ b/x	Thu Jan 01 00:00:00 1970 +0000
   @@ -0,0 +1,1 @@
   +hello world
+
+Editing a hunk puts you back on that hunk when done editing (issue5041)
+To do that, we change two lines in a file, pretend to edit the second line,
+exit, toggle the line selected at the end of the edit and commit.
+The first line should be recorded if we were put on the second line at the end
+of the edit.
+
+  $ hg update -C .
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ echo "foo" > x
+  $ echo "hello world" >> x
+  $ echo "bar" >> x
+  $ cat <<EOF >testModeCommands
+  > f
+  > KEY_DOWN
+  > KEY_DOWN
+  > KEY_DOWN
+  > KEY_DOWN
+  > e
+  > TOGGLE
+  > X
+  > EOF
+  $ printf "printf 'editor ran\n'; exit 0" > editor.sh
+  $ HGEDITOR="\"sh\" \"`pwd`/editor.sh\"" hg commit  -i -m "edit hunk" -d "0 0"
+  editor ran
+  $ hg cat -r . x
+  foo
+  hello world
+
+