hgk: don't honor whitespace and format-changing diffopts

The diff-tree command is a plumbing command in Git, which means it is expected
to have a stable output format. Ensure that our output is stable too.

hgext/hgk.py

@@ -95,8 +95,10 b' def difftree(ui, repo, node1=None, node2'
             if opts['pretty']:
                 catcommit(ui, repo, node2, "")
             m = scmutil.match(repo[node1], files)
+            diffopts = patch.difffeatureopts(ui)
+            diffopts.git = True
             chunks = patch.diff(repo, node1, node2, match=m,
-                                opts=patch.diffopts(ui, {'git': True}))
+                                opts=diffopts)
             for chunk in chunks:
                 ui.write(chunk)
         else:

tests/test-hgk.t

@@ -16,5 +16,32 b' Minimal hgk check'
   phase draft
   
   adda
+  $ echo b > b
+  $ hg ci -Am addb
+  adding b
+  $ hg log -T '{node}\n'
+  102a90ea7b4a3361e4082ed620918c261189a36a
+  07f4944404050f47db2e5c5071e0e84e7a27bba9
+
+  $ hg debug-diff-tree 07f494440405 102a90ea7b4a
+  :000000 100664 000000000000 1e88685f5dde N	b	b
+  $ hg debug-diff-tree 07f494440405 102a90ea7b4a --patch
+  diff --git a/b b/b
+  new file mode 100644
+  --- /dev/null
+  +++ b/b
+  @@ -0,0 +1,1 @@
+  +b
+
+Ensure that diff-tree output isn't affected by diffopts
+  $ hg --config diff.noprefix=True debug-diff-tree 07f494440405 102a90ea7b4a
+  :000000 100664 000000000000 1e88685f5dde N	b	b
+  $ hg --config diff.noprefix=True debug-diff-tree --patch 07f494440405 102a90ea7b4a
+  diff --git a/b b/b
+  new file mode 100644
+  --- /dev/null
+  +++ b/b
+  @@ -0,0 +1,1 @@
+  +b
 
   $ cd ..