mq: create non-lossy patches, also with custom global diff configuration stable

mq: create non-lossy patches, also with custom global diff configuration

Users with custom [diff] configuration most certainly didn't intend it to make
mq lose changes. It could:

 * git is handled perfectly fine.

 * nobinary could make mq leave some files out from the patches.

 * noprefix could make mq itself (and probably also other tools) fail to apply
   patches without the usual a/b prefix.

 * ignorews, ignorewsamount, or ignoreblanklines could create patches with
   missing whitespace that could fail to apply correctly.

Thus, when refreshing patches, use patch.difffeatureopts, optionally with git
as before, but without the config options for whitespace and format changing
that most likely will cause loss or problems.

(patch.diffopts is just patch.difffeatureopts with all options enabled and can
be replaced with that.)

--- a/hgext/mq.py	Mon Sep 11 00:42:22 2017 +0200
+++ b/hgext/mq.py	Mon Sep 11 00:42:24 2017 +0200
@@ -503,8 +503,11 @@
         self.guardsdirty = False
         self.activeguards = None
 
-    def diffopts(self, opts=None, patchfn=None):
-        diffopts = patchmod.diffopts(self.ui, opts)
+    def diffopts(self, opts=None, patchfn=None, plain=False):
+        """Return diff options tweaked for this mq use, possibly upgrading to
+        git format, and possibly plain and without lossy options."""
+        diffopts = patchmod.difffeatureopts(self.ui, opts,
+            git=True, whitespace=not plain, formatchanging=not plain)
         if self.gitmode == 'auto':
             diffopts.upgrade = True
         elif self.gitmode == 'keep':
@@ -1177,7 +1180,7 @@
         date = opts.get('date')
         if date:
             date = util.parsedate(date)
-        diffopts = self.diffopts({'git': opts.get('git')})
+        diffopts = self.diffopts({'git': opts.get('git')}, plain=True)
         if opts.get('checkname', True):
             self.checkpatchname(patchfn)
         inclsubs = checksubstate(repo)
@@ -1642,7 +1645,8 @@
                 substatestate = repo.dirstate['.hgsubstate']
 
             ph = patchheader(self.join(patchfn), self.plainmode)
-            diffopts = self.diffopts({'git': opts.get('git')}, patchfn)
+            diffopts = self.diffopts({'git': opts.get('git')}, patchfn,
+                                     plain=True)
             if newuser:
                 ph.setuser(newuser)
             if newdate:

--- a/tests/test-mq-git.t	Mon Sep 11 00:42:22 2017 +0200
+++ b/tests/test-mq-git.t	Mon Sep 11 00:42:24 2017 +0200
@@ -235,13 +235,35 @@
   # Date 0 0
   # Parent  cf0bfe72686a47d8d7d7b4529a3adb8b0b449a9f
   
+  diff -r cf0bfe72686a -r fb9c4422b0f3 a
+  --- a/a
+  +++ b/a
+  @@ -1,1 +1,1 @@
+  -a
+  + a
   $ cat .hg/patches/diff
   # HG changeset patch
   # Date 0 0
   # Parent  fb9c4422b0f37dd576522dd9a3f99b825c177efe
   
-  diff --git b b
-  Binary file b has changed
+  diff --git a/a b/a
+  --- a/a
+  +++ b/a
+  @@ -1,1 +1,1 @@
+  - a
+  +  a
+  diff --git a/b b/b
+  index 78981922613b2afb6025042ff6bd878ac1994e85..f76dd238ade08917e6712764a16a22005a50573d
+  GIT binary patch
+  literal 1
+  Ic${MZ000310RR91
+  
+  diff --git a/c b/c
+  --- a/c
+  +++ b/c
+  @@ -1,1 +1,2 @@
+   a
+  +
 
   $ cd ..