graft: move commit info building

This moves the logic for generating the commit metadata ahead of the
merge operation.  The only purposae of this patch is to make
subsequent patches easier to read, and there should be no behavior
changes.

mercurial/commands.py

@@ -2837,6 +2837,20 b' def graft(ui, repo, *revs, **opts):'
             if opts.get('dry_run'):
                 continue
 
+            source = ctx.extra().get('source')
+            if not source:
+                source = ctx.hex()
+            extra = {'source': source}
+            user = ctx.user()
+            if opts.get('user'):
+                user = opts['user']
+            date = ctx.date()
+            if opts.get('date'):
+                date = opts['date']
+            message = ctx.description()
+            if opts.get('log'):
+                message += '\n(grafted from %s)' % ctx.hex()
+
             # we don't merge the first commit when continuing
             if not cont:
                 # perform the graft merge with p1(rev) as 'ancestor'
@@ -2865,19 +2879,6 b' def graft(ui, repo, *revs, **opts):'
             cmdutil.duplicatecopies(repo, ctx.rev(), ctx.p1().rev())
 
             # commit
-            source = ctx.extra().get('source')
-            if not source:
-                source = ctx.hex()
-            extra = {'source': source}
-            user = ctx.user()
-            if opts.get('user'):
-                user = opts['user']
-            date = ctx.date()
-            if opts.get('date'):
-                date = opts['date']
-            message = ctx.description()
-            if opts.get('log'):
-                message += '\n(grafted from %s)' % ctx.hex()
             node = repo.commit(text=message, user=user,
                         date=date, extra=extra, editor=editor)
             if node is None: