shelve: changes getting opts values by get method

shelve: changes getting opts values by get method

When shelve is used by another extension that doesn't
provide all necessary values in opts shelve raises
KeyError exception. This patch fixes this by getting
values from opts dictionary with get method.

--- a/hgext/shelve.py	Sat Feb 27 21:15:16 2016 -0800
+++ b/hgext/shelve.py	Wed Mar 09 08:21:57 2016 +0100
@@ -290,10 +290,10 @@
     else:
         desc = '(changes in empty repository)'
 
-    if not opts['message']:
+    if not opts.get('message'):
         opts['message'] = desc
 
-    name = opts['name']
+    name = opts.get('name')
 
     lock = tr = None
     try:
@@ -540,7 +540,7 @@
 
 def unshelvecleanup(ui, repo, name, opts):
     """remove related files after an unshelve"""
-    if not opts['keep']:
+    if not opts.get('keep'):
         for filetype in 'hg patch'.split():
             shelvedfile(repo, name, filetype).movetobackup()
         cleanupoldbackups(repo)
@@ -630,8 +630,8 @@
         return _dounshelve(ui, repo, *shelved, **opts)
 
 def _dounshelve(ui, repo, *shelved, **opts):
-    abortf = opts['abort']
-    continuef = opts['continue']
+    abortf = opts.get('abort')
+    continuef = opts.get('continue')
     if not abortf and not continuef:
         cmdutil.checkunfinished(repo)
 
@@ -850,7 +850,7 @@
         ('stat', set(['stat', 'list'])),
     ]
     def checkopt(opt):
-        if opts[opt]:
+        if opts.get(opt):
             for i, allowable in allowables:
                 if opts[i] and opt not in allowable:
                     raise error.Abort(_("options '--%s' and '--%s' may not be "