cat: avoid round tripping **opts -> byteskwargs -> strkwargs

Some internal users still want byteskwargs, so they are serviced in place.  Once
this pattern of changing types is eliminated everywhere, the remaining internal
uses can be cleaned up individually (hopefully).

mercurial/commands.py

@@ -1794,25 +1794,22 b' def cat(ui, repo, file1, *pats, **opts):'
 
     Returns 0 on success.
     """
-    opts = pycompat.byteskwargs(opts)
-    rev = opts.get(b'rev')
+    rev = opts.get('rev')
     if rev:
         repo = scmutil.unhidehashlikerevs(repo, [rev], b'nowarn')
     ctx = logcmdutil.revsingle(repo, rev)
-    m = scmutil.match(ctx, (file1,) + pats, opts)
-    fntemplate = opts.pop(b'output', b'')
+    m = scmutil.match(ctx, (file1,) + pats, pycompat.byteskwargs(opts))
+    fntemplate = opts.pop('output', b'')
     if cmdutil.isstdiofilename(fntemplate):
         fntemplate = b''
 
     if fntemplate:
-        fm = formatter.nullformatter(ui, b'cat', opts)
+        fm = formatter.nullformatter(ui, b'cat', pycompat.byteskwargs(opts))
     else:
         ui.pager(b'cat')
-        fm = ui.formatter(b'cat', opts)
+        fm = ui.formatter(b'cat', pycompat.byteskwargs(opts))
     with fm:
-        return cmdutil.cat(
-            ui, repo, ctx, m, fm, fntemplate, b'', **pycompat.strkwargs(opts)
-        )
+        return cmdutil.cat(ui, repo, ctx, m, fm, fntemplate, b'', **opts)
 
 
 @command(