Initial Contribution

pager.py

@@ -0,0 +1,84 @@
+#
+# Copyright (C) 2008 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import select
+import sys
+
+active = False
+
+def RunPager(globalConfig):
+  global active
+
+  if not os.isatty(0):
+    return
+  pager = _SelectPager(globalConfig)
+  if pager == '' or pager == 'cat':
+    return
+
+  # This process turns into the pager; a child it forks will
+  # do the real processing and output back to the pager. This
+  # is necessary to keep the pager in control of the tty.
+  #
+  try:
+    r, w = os.pipe()
+    pid = os.fork()
+    if not pid:
+      os.dup2(w, 1)
+      os.dup2(w, 2)
+      os.close(r)
+      os.close(w)
+      active = True
+      return
+
+    os.dup2(r, 0)
+    os.close(r)
+    os.close(w)
+
+    _BecomePager(pager)
+  except Exception:
+    print >>sys.stderr, "fatal: cannot start pager '%s'" % pager
+    os.exit(255)
+
+def _SelectPager(globalConfig):
+  try:
+    return os.environ['GIT_PAGER']
+  except KeyError:
+    pass
+
+  pager = globalConfig.GetString('core.pager')
+  if pager:
+    return pager
+
+  try:
+    return os.environ['PAGER']
+  except KeyError:
+    pass
+
+  return 'less'
+
+def _BecomePager(pager):
+  # Delaying execution of the pager until we have output
+  # ready works around a long-standing bug in popularly
+  # available versions of 'less', a better 'more'.
+  #
+  a, b, c = select.select([0], [], [0])
+
+  os.environ['LESS'] = 'FRSX'
+
+  try:
+    os.execvp(pager, [pager])
+  except OSError, e:
+    os.execv('/bin/sh', ['sh', '-c', pager])