copy: add experimetal support for unmarking committed copies The simplest way I'm aware of to unmark a file as copied after committing is this: hg uncommit --keep <dest> hg forget <dest> hg add <dest> hg amend This patch teaches `hg copy --forget` a `-r` argument to simplify that into: hg copy --forget --at-rev . <dest> In addition to being simpler, it doesn't touch the working copy, so it can easily be used even if the destination file has been modified in the working copy. I'll teach `hg copy` without `--forget` to work with `--at-rev` next. Differential Revision: https://phab.mercurial-scm.org/D8030

--- a/mercurial/commands.py	Fri Dec 20 15:50:13 2019 -0800
+++ b/mercurial/commands.py	Tue Jan 28 14:07:57 2020 -0800
@@ -2312,6 +2312,13 @@
         (b'', b'forget', None, _(b'unmark a file as copied')),
         (b'A', b'after', None, _(b'record a copy that has already occurred')),
         (
+            b'',
+            b'at-rev',
+            b'',
+            _(b'unmark copies in the given revision (EXPERIMENTAL)'),
+            _(b'REV'),
+        ),
+        (
             b'f',
             b'force',
             None,