[PATCH 02 of 10 V4] context: drop a redundant fast path in introrev

[Boris Feld]

# HG changeset patch
# User Boris Feld <boris.feld at octobus.net>
# Date 1538635201 -7200
#      Thu Oct 04 08:40:01 2018 +0200
# Node ID afeaa54d6b18c6582e461a65000f506bc1d7b9d8
# Parent  8ae36e75e785542f415e0b1daa6f2c840542e17e
# EXP-Topic copy-perf
# Available At https://bitbucket.org/octobus/mercurial-devel/
#              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r afeaa54d6b18
context: drop a redundant fast path in introrev

Now that _adjustlinkrev fast path this case itself, we no longer need an extra
conditional.

A nice side effect is that we are no longer calling `self.rev()`. In case
where `_descendantrev` is set, calling `self.rev` will trigger a potentially
expensive `_adjustlinkrev` call. So blindly calling `self.rev()` to avoid
another `_adjustlinkrev` call can be counterproductive.

Note that `_descendantrev` is currently never taken into account in `introrev`
so far which is wrong. We'll fix that in changeset later in this series.

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -779,7 +779,7 @@ class basefilectx(object):
         lkr = self.linkrev()
         attrs = vars(self)
         noctx = not (r'_changeid' in attrs or r'_changectx' in attrs)
-        if noctx or self.rev() == lkr:
+        if noctx:
             return self.linkrev()
         return self._adjustlinkrev(self.rev(), inclusive=True)