pager: exec pager using /bin/sh -c

This mimics the behavior of popen() and ensures setting the pager to something
like "LESS=FSRX less" will work.

hgext/pager.py

@@ -1,88 +1,95 b''
 # pager.py - display output using a pager
 #
 # Copyright 2008 David Soria Parra <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 #
 # To load the extension, add it to your .hgrc file:
 #
 #   [extension]
 #   pager =
 #
 # Run "hg help pager" to get info on configuration.
 
 '''browse command output with an external pager
 
 To set the pager that should be used, set the application variable::
 
   [pager]
   pager = LESS='FSRX' less
 
 If no pager is set, the pager extensions uses the environment variable
 $PAGER. If neither pager.pager, nor $PAGER is set, no pager is used.
 
 If you notice "BROKEN PIPE" error messages, you can disable them by
 setting::
 
   [pager]
   quiet = True
 
 You can disable the pager for certain commands by adding them to the
 pager.ignore list::
 
   [pager]
   ignore = version, help, update
 
 You can also enable the pager only for certain commands using
 pager.attend. Below is the default list of commands to be paged::
 
   [pager]
   attend = annotate, cat, diff, export, glog, log, qdiff
 
 Setting pager.attend to an empty value will cause all commands to be
 paged.
 
 If pager.attend is present, pager.ignore will be ignored.
 
 To ignore global commands like :hg:`version` or :hg:`help`, you have
 to specify them in the global .hgrc
 '''
 
-import sys, os, signal, shlex
+import sys, os, signal, shlex, errno
 from mercurial import dispatch, util, extensions
 
 def _runpager(p):
     if not hasattr(os, 'fork'):
         sys.stderr = sys.stdout = util.popen(p, 'wb')
         return
     fdin, fdout = os.pipe()
     pid = os.fork()
     if pid == 0:
         os.close(fdin)
         os.dup2(fdout, sys.stdout.fileno())
         os.dup2(fdout, sys.stderr.fileno())
         os.close(fdout)
         return
     os.dup2(fdin, sys.stdin.fileno())
     os.close(fdin)
     os.close(fdout)
-    args = shlex.split(p)
-    os.execvp(args[0], args)
+    try:
+        os.execvp('/bin/sh', ['/bin/sh', '-c', p])
+    except OSError, e:
+        if e.errno == errno.ENOENT:
+            # no /bin/sh, try executing the pager directly
+            args = shlex.split(p)
+            os.execvp(args[0], args)
+        else:
+            raise
 
 def uisetup(ui):
     def pagecmd(orig, ui, options, cmd, cmdfunc):
         p = ui.config("pager", "pager", os.environ.get("PAGER"))
         if p and sys.stdout.isatty() and '--debugger' not in sys.argv:
             attend = ui.configlist('pager', 'attend', attended)
             if (cmd in attend or
                 (cmd not in ui.configlist('pager', 'ignore') and not attend)):
                 ui.setconfig('ui', 'interactive', False)
                 _runpager(p)
                 if ui.configbool('pager', 'quiet'):
                     signal.signal(signal.SIGPIPE, signal.SIG_DFL)
         return orig(ui, options, cmd, cmdfunc)
 
     extensions.wrapfunction(dispatch, '_runcommand', pagecmd)
 
 attended = ['annotate', 'cat', 'diff', 'export', 'glog', 'log', 'qdiff']