Pager extension: switch it off if --debugger is set

The pager is preventing the debugger prompt and much of the
debugger output to be refreshed. Moreover the pager does not
make sense when debugging line by line.

(This supersedes the similar ui.debugflag patch. Disabling
the pager for debug output doesn't make that much sense,
as this is actually when the pager might be useful.)

hgext/pager.py

@@ -29,7 +29,7 b' import sys, os, signal'
 
 def uisetup(ui):
     p = ui.config("pager", "pager", os.environ.get("PAGER"))
-    if p and sys.stdout.isatty() and not ui.debugflag:
+    if p and sys.stdout.isatty() and '--debugger' not in sys.argv:
         if ui.configbool('pager', 'quiet'):
             signal.signal(signal.SIGPIPE, signal.SIG_DFL)
         sys.stderr = sys.stdout = os.popen(p, "wb")