[PATCH 2 of 9 V2] revlog: clarify flagprocessor documentation

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1490885988 25200
#      Thu Mar 30 07:59:48 2017 -0700
# Node ID 31aa38709dbd983b87302a0f24f4cf78a138ae83
# Parent  4a3f09c00a850667225b56d4aa0069e8e8233281
# Available At https://bitbucket.org/quark-zju/hg-draft
#              hg pull https://bitbucket.org/quark-zju/hg-draft -r 31aa38709dbd
revlog: clarify flagprocessor documentation

The words "text", "newtext", "bool" could be confusing. Use explicit "text"
or "rawtext" and document more about the "bool".

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -89,9 +89,15 @@ def addflagprocessor(flag, processor):
     - flagprocessors must be 3-tuples of functions (read, write, raw) with the
       following signatures:
-          - (read)  f(self, text) -> newtext, bool
-          - (write) f(self, text) -> newtext, bool
-          - (raw)   f(self, text) -> bool
+          - (read)  f(self, rawtext) -> text, bool
+          - (write) f(self, text) -> rawtext, bool
+          - (raw)   f(self, rawtext) -> bool
+      "text" is presented to the user. "rawtext" is stored in revlog data, not
+      directly visible to the user.
       The boolean returned by these transforms is used to determine whether
-      'newtext' can be used for hash integrity checking.
+      the returned text can be used for hash integrity checking. For example,
+      if "write" returns False, then "text" is used to generate hash. If
+      "write" returns True, that basically means "rawtext" returned by "write"
+      should be used to generate hash. Usually, "write" and "read" return
+      different booleans. And "raw" returns a same boolean as "write".
 
       Note: The 'raw' transform is used for changegroup generation and in some