amend: support "history-editing-backup" config option

Now, amend is in the list of those history editing commands
which support `history-editing-backup` config option.
If you don't want to store any backup then just use this config.
[ui]
hisotry-editing-backup = False

Current status of list of history editing commands which support
this config:
1. histedit
2. rebase
3. amend

Differential Revision: https://phab.mercurial-scm.org/D3968

mercurial/cmdutil.py

@@ -2556,8 +2556,10 b' def amend(ui, repo, old, extra, pats, op'
         obsmetadata = None
         if opts.get('note'):
             obsmetadata = {'note': encoding.fromlocal(opts['note'])}
+        backup = ui.configbool('ui', 'history-editing-backup')
         scmutil.cleanupnodes(repo, mapping, 'amend', metadata=obsmetadata,
-                             fixphase=True, targetphase=commitphase)
+                             fixphase=True, targetphase=commitphase,
+                             backup=backup)
 
         # Fixing the dirstate because localrepo.commitctx does not update
         # it. This is rather convenient because we did not need to update

tests/test-amend.t

@@ -331,3 +331,37 b' working directory should be all clean (w'
   ? missing_content2_content2-untracked
   ? missing_content2_content3-untracked
   ? missing_missing_content3-untracked
+
+==========================================
+Test history-editing-backup config option|
+==========================================
+  $ hg init $TESTTMP/repo4
+  $ cd $TESTTMP/repo4
+  $ echo a>a
+  $ hg ci -Aqma
+  $ echo oops>b
+  $ hg ci -Aqm "b"
+  $ echo partiallyfixed > b
+
+#if obsstore-off
+  $ hg amend
+  saved backup bundle to $TESTTMP/repo4/.hg/strip-backup/95e899acf2ce-f11cb050-amend.hg
+When history-editing-backup config option is set:
+  $ cat << EOF >> $HGRCPATH
+  > [ui]
+  > history-editing-backup = False
+  > EOF
+  $ echo fixed > b
+  $ hg amend
+
+#else
+  $ hg amend
+When history-editing-backup config option is set:
+  $ cat << EOF >> $HGRCPATH
+  > [ui]
+  > history-editing-backup = False
+  > EOF
+  $ echo fixed > b
+  $ hg amend
+
+#endif