Fix prompt exporting escaped characters, opt into PS1 mod.

go/env.py

 #!/usr/bin/env python
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Can be used to point environment variable to hermetic Go toolset.
 
 Usage (on linux and mac):
 $ eval `./env.py`
 $ go version
@@ skipping 14 matching lines @@
 # Do not want to mess with sys.path, load the module directly.
 bootstrap = imp.load_source(
     'bootstrap', os.path.join(os.path.dirname(__file__), 'bootstrap.py'))
 
 old = os.environ.copy()
 new = bootstrap.prepare_go_environ()
 
 if len(sys.argv) == 1:
   for key, value in sorted(new.iteritems()):
     if old.get(key) != value:
-      print 'export %s=%s' % (key, pipes.quote(value))
+      # Replace special characters with their escaped form. This will allow them

[mithro, 2016/07/07 02:09:39]

Can you move this into a function?

[dnj (Google), 2016/07/07 03:43:30]

Done.

+      # to be interpreted by the shell using the $'...' notation. We will only
+      # use the $'...' notation if there was an escaped character in the string.
+      orig_value = value
+      for f, r in (
+          ('\n', r'\n'),

[mithro, 2016/07/07 02:09:38]

This is kind of confusing, I think

 ('\n', '\\n') 

Would probably be clearer.

[dnj (Google), 2016/07/07 03:43:30]

Done.

+          ('\b', r'\b'),
+          ('\r', r'\r'),
+          ('\t', r'\t'),
+          ('\v', r'\v')):
+        value = value.replace(f, r)
+      print 'export %s=%s%s' % (key, ('$') if orig_value != value else (''),
+                                pipes.quote(value))
 else:
   exe = sys.argv[1]
   if exe == 'python':
     exe = sys.executable
   else:
     # Help Windows to find the executable in new PATH, do it only when
     # executable is referenced by name (and not by path).
     if os.sep not in exe:
       exe = bootstrap.find_executable(exe, [bootstrap.WORKSPACE])
   sys.exit(subprocess.call([exe] + sys.argv[2:], env=new))