narrow: don't resurrect old commits when narrowing (don't strip obsmarkers)

If you have an old obsolescence-chain of commits that has been pruned
and you narrow your repo so that some of those commits get stripped
(because they affected the removed paths), then we would currently
resurrect the commit that came before (along the obsmarker chain) the
last stripped commit. That happens by the usual rules for
obsmarker-stripping. However, it's quite surprising when it happens
when you narrow your repo. This patch makes narrowing not strip
obsmarkers.

Differential Revision: https://phab.mercurial-scm.org/D5364

hgext/narrow/narrowcommands.py

@@ -215,7 +215,9 b' def _narrow(ui, repo, remote, commoninc,'
                 urev = max(repo.revs('(::%n) - %ln + null',
                                      repo['.'].node(), visibletostrip))
                 hg.clean(repo, urev)
-            repair.strip(ui, unfi, tostrip, topic='narrow')
+            overrides = {('devel', 'strip-obsmarkers'): False}
+            with ui.configoverride(overrides, 'narrow'):
+                repair.strip(ui, unfi, tostrip, topic='narrow')
 
         todelete = []
         for f, f2, size in repo.store.datafiles():

tests/test-narrow.t

@@ -214,6 +214,29 b' Updates to nullid if necessary'
   000000000000
   $ cd ..
 
+Narrowing doesn't resurrect old commits (unlike what regular `hg strip` does)
+  $ hg clone --narrow ssh://user@dummy/master narrow-obsmarkers --include d0 --include d3 -q
+  $ cd narrow-obsmarkers
+  $ echo a >> d0/f2
+  $ hg add d0/f2
+  $ hg ci -m 'modify d0/'
+  $ echo a >> d3/f2
+  $ hg add d3/f2
+  $ hg commit --amend -m 'modify d0/ and d3/'
+  $ hg log -T "{rev}: {desc}\n"
+  5: modify d0/ and d3/
+  3: add d10/f
+  2: add d3/f
+  1: add d2/f
+  0: add d0/f
+  $ hg tracked --removeinclude d3 --force-delete-local-changes -q
+  $ hg log -T "{rev}: {desc}\n"
+  3: add d10/f
+  2: add d3/f
+  1: add d2/f
+  0: add d0/f
+  $ cd ..
+
 Can remove last include, making repo empty
   $ hg clone --narrow ssh://user@dummy/master narrow-empty --include d0 -r 5
   adding changesets