commit: write last-message.txt with no content modifications.

This assumes the user will use either a sane editor (anything but
Notepad) or the same editor again: even Notepad should be able to read
what it previously wrote.

mercurial/localrepo.py

@@ -837,12 +837,10 b' class localrepository(repo.repository):'
                 subrepo.writestate(self, state)
 
             # Save commit message in case this transaction gets rolled back
-            # (e.g. by a pretxncommit hook).  (Save in text mode in case a
-            # Windows user wants to edit it with Notepad.  Normalize
-            # trailing whitespace so the file always looks the same --
-            # makes testing easier.)
-            msgfile = self.opener('last-message.txt', 'w')
-            msgfile.write(cctx._text.rstrip() + '\n')
+            # (e.g. by a pretxncommit hook).  Leave the content alone on
+            # the assumption that the user will use the same editor again.
+            msgfile = self.opener('last-message.txt', 'wb')
+            msgfile.write(cctx._text)
             msgfile.close()
 
             try:

tests/test-rollback

@@ -22,7 +22,7 b' hg branch'
 
 echo '% Test issue 1635 (commit message saved)'
 echo '.hg/last-message.txt:'
-cat .hg/last-message.txt
+cat .hg/last-message.txt ; echo
 
 echo % Test rollback of hg before issue 902 was fixed
 hg commit -m "test3"
@@ -35,7 +35,7 b" echo '% rollback by pretxncommit saves c"
 echo a >> a
 hg --config hooks.pretxncommit=/bin/false commit -m"precious commit message"
 echo '.hg/last-message.txt:'
-cat .hg/last-message.txt
+cat .hg/last-message.txt ; echo
 
 echo '% same thing, but run $EDITOR'
 cat > $HGTMP/editor <<'__EOF__'