[PATCH 3 of 3 RFC V2] setup: use changes since latest tag instead of just distance

[Siddharth Agarwal]

# HG changeset patch
# User Siddharth Agarwal <sid0 at fb.com>
# Date 1418427088 28800
#      Fri Dec 12 15:31:28 2014 -0800
# Node ID b00b4bbaefac444a40dcadb2e019c4c6b463d9d6
# Parent  71df59b4066e7df2b38c81376fb4152c5735e311
setup: use changes since latest tag instead of just distance

For a Mercurial built on the merge from stable into default right after 3.2.2
was released -- 19ebd2f88fc7 -- the version number produced was "3.2.2+4". This
is potentially misleading, since in reality the built Mercurial includes many
more changes compared to 3.2.2.

Change the versioning scheme so that we take into consideration all the changes
present in the current revision that aren't present in the latest tag. For
19ebd2f88fc7 the new versioning scheme results in a version number of
"3.2.2+256". This gives users a much better idea of how many changes have
actually happened since the latest release.

Since changessincelatesttag is always greater than or equal to the
latesttagdistance, this will produce version numbers that are always greater
than or equal to the old scheme. Thus there's minimal compatibility risk.

diff --git a/setup.py b/setup.py
--- a/setup.py
+++ b/setup.py
@@ -196,9 +196,13 @@
         if hgid.endswith('+'): # propagate the dirty status to the tag
             version += '+'
     else: # no tag found
-        cmd = [sys.executable, 'hg', 'parents', '--template',
-               '{latesttag}+{latesttagdistance}-']
-        version = runhg(cmd, env) + hgid
+        ltagcmd = [sys.executable, 'hg', 'parents', '--template',
+                   '{latesttag}']
+        ltag = runhg(ltagcmd, env)
+        changessincecmd = [sys.executable, 'hg', 'log', '-T', 'x\n', '-r',
+                           "only(.,'%s')" % ltag]
+        changessince = len(runhg(changessincecmd, env).splitlines())
+        version = '%s+%s-%s' % (ltag, changessince, hgid)
     if version.endswith('+'):
         version += time.strftime('%Y%m%d')
 elif os.path.exists('.hg_archival.txt'):