lfs: fix committing deleted files caused by e0a1b9ee93cd

lfs: fix committing deleted files caused by e0a1b9ee93cd

e0a1b9ee93cd (lfs: add a repo requirement for this extension once an lfs
file is committed) introduced a regression that prevents committing file
deletion.  This patch fixes that.

Differential Revision: https://phab.mercurial-scm.org/D1717

--- a/hgext/lfs/__init__.py	Mon Dec 18 13:15:10 2017 -0500
+++ b/hgext/lfs/__init__.py	Mon Dec 18 14:37:00 2017 -0800
@@ -124,7 +124,7 @@
             if 'lfs' not in repo.requirements:
                 ctx = repo[kwargs['node']]
                 # TODO: is there a way to just walk the files in the commit?
-                if any(ctx[f].islfs() for f in ctx.files()):
+                if any(ctx[f].islfs() for f in ctx.files() if f in ctx):
                     repo.requirements.add('lfs')
                     repo._writerequirements()
 

--- a/tests/test-lfs.t	Mon Dec 18 13:15:10 2017 -0500
+++ b/tests/test-lfs.t	Mon Dec 18 14:37:00 2017 -0800
@@ -680,3 +680,12 @@
 
   $ hg -R convert_lfs2 config --debug extensions | grep lfs
   $TESTTMP/convert_lfs2/.hg/hgrc:*: extensions.lfs= (glob)
+
+Committing deleted files works:
+
+  $ hg init $TESTTMP/repo-del
+  $ cd $TESTTMP/repo-del
+  $ echo 1 > A
+  $ hg commit -m 'add A' -A A
+  $ hg rm A
+  $ hg commit -m 'rm A'