extdiff: escape filenames with vim/DirDiff and make quoting work with Windows

Use vim function fnameescape() on filenames.
Use double quotes for arguments so cmd.exe is happy.

contrib/win32/mercurial.ini

@@ -71,7 +71,7 editor = notepad
 ;cmd.bc3diff = C:\Program Files\Beyond Compare 3\BCompare.exe
 ;cmd.vdiff = C:\Progra~1\TortoiseSVN\bin\TortoiseMerge.exe
 ;cmd.vimdiff = gvim.exe
-;opts.vimdiff = -f '+next' '+execute "DirDiff ".argv(0)." ".argv(1)'
+;opts.vimdiff = -f "+next" "+execute 'DirDiff' fnameescape(argv(0)) fnameescape(argv(1))"
 
 
 [hgk]

hgext/extdiff.py

@@ -33,7 +33,8 you do not need to type :hg:`extdiff -p
   # (see http://www.vim.org/scripts/script.php?script_id=102) Non
   # English user, be sure to put "let g:DirDiffDynamicDiffText = 1" in
   # your .vimrc
-  vimdiff = gvim -f '+next' '+execute "DirDiff" argv(0) argv(1)'
+  vimdiff = gvim -f "+next" \\
+            "+execute 'DirDiff' fnameescape(argv(0)) fnameescape(argv(1))"
 
 Tool arguments can include variables that are expanded at runtime::
 

tests/test-extension.t

@@ -301,7 +301,8 Extension module help vs command help:
     # (see http://www.vim.org/scripts/script.php?script_id=102) Non
     # English user, be sure to put "let g:DirDiffDynamicDiffText = 1" in
     # your .vimrc
-    vimdiff = gvim -f '+next' '+execute "DirDiff" argv(0) argv(1)'
+    vimdiff = gvim -f "+next" \
+              "+execute 'DirDiff' fnameescape(argv(0)) fnameescape(argv(1))"
   
   Tool arguments can include variables that are expanded at runtime: