test-context: add test for performing a diff on a memctx

We now see the first result of all that refactoring of memctx: we can now diff
against a memctx.

tests/test-context.py

@@ -1,48 +1,52 b''
 import os
 from mercurial import hg, ui, context, encoding
 
 u = ui.ui()
 
 repo = hg.repository(u, 'test1', create=1)
 os.chdir('test1')
 
 # create 'foo' with fixed time stamp
 f = open('foo', 'w')
 f.write('foo\n')
 f.close()
 os.utime('foo', (1000, 1000))
 
 # add+commit 'foo'
 repo[None].add(['foo'])
 repo.commit(text='commit1', date="0 0")
 
 print "workingfilectx.date =", repo[None]['foo'].date()
 
 # test memctx with non-ASCII commit message
 
 def filectxfn(repo, memctx, path):
     return context.memfilectx(repo, "foo", "")
 
 ctx = context.memctx(repo, ['tip', None],
                      encoding.tolocal("Gr\xc3\xbcezi!"),
                      ["foo"], filectxfn)
 ctx.commit()
 for enc in "ASCII", "Latin-1", "UTF-8":
     encoding.encoding = enc
     print "%-8s: %s" % (enc, repo["tip"].description())
 
 # test performing a status
 
 def getfilectx(repo, memctx, f):
     fctx = memctx.parents()[0][f]
     data, flags = fctx.data(), fctx.flags()
     if f == 'foo':
         data += 'bar\n'
     return context.memfilectx(repo, f, data, 'l' in flags, 'x' in flags)
 
 ctxa = repo.changectx(0)
-ctxb = context.memctx(repo, [ctxa.node(), None],
-                      "test diff",
-                      ["foo"], getfilectx)
+ctxb = context.memctx(repo, [ctxa.node(), None], "test diff", ["foo"],
+                      getfilectx, ctxa.user(), ctxa.date())
 
 print ctxb.status(ctxa)
+
+# test performing a diff on a memctx
+
+for d in ctxb.diff(ctxa, git=True):
+    print d

tests/test-context.py.out

@@ -1,5 +1,13 b''
 workingfilectx.date = (1000, 0)
 ASCII   : Gr?ezi!
 Latin-1 : Gr�ezi!
 UTF-8   : Grüezi!
 (['foo'], [], [], [], [], [], [])
+diff --git a/foo b/foo
+
+--- a/foo
++++ b/foo
+@@ -1,1 +1,2 @@
+ foo
++bar
+