# HG changeset patch
# User Jun Wu <quark@fb.com>
# Date 1490588822 25200
# Node ID 0be96ac9199ad8c7d9280d1b9afd57d349613fe2
# Parent  00e569a2da975bdf80e42e15c96cafd258476095
rcutil: add a method to convert environment variables to config items

Handling config and environ priorities has been messy. Partially because we
don't have config layers - you either get all configs (sys + user), or none.

Ideally, environ like $EDITOR, $PAGER should be able to override the system
configs "ui.editor", "pager.pager". This patch provides the ability to
convert them into config items, so they can be inserted into the middle
config layer between system rc and user rc.

diff -r 00e569a2da97 -r 0be96ac9199a mercurial/rcutil.py
--- a/mercurial/rcutil.py	Sun Mar 26 21:04:29 2017 -0700
+++ b/mercurial/rcutil.py	Sun Mar 26 21:27:02 2017 -0700
@@ -32,6 +32,28 @@
         return [join(p, f) for f, k in osutil.listdir(p) if f.endswith('.rc')]
     return [p]
 
+def envrcitems(env=None):
+    '''Return [(section, name, value, source)] config items.
+
+    The config items are extracted from environment variables specified by env,
+    used to override systemrc, but not userrc.
+
+    If env is not provided, encoding.environ will be used.
+    '''
+    if env is None:
+        env = encoding.environ
+    checklist = [
+        ('EDITOR', 'ui', 'editor'),
+        ('VISUAL', 'ui', 'editor'),
+        ('PAGER', 'pager', 'pager'),
+    ]
+    result = []
+    for envname, section, configname in checklist:
+        if envname not in env:
+            continue
+        result.append((section, configname, env[envname], '$%s' % envname))
+    return result
+
 def defaultrcpath():
     '''return rc paths in default.d'''
     path = []