Meta/onemerge: force C locale on comm

The script has 'comm' compare two 'git branch --list' output, which
is strictly ASCII/lexicographic order.  In en_US locale, for example,
the 'git branch --list' output order may not look sorted, e.g.
'pack-objects' may sort before or after 'packfile'.

onemerge.sh

@@ -2,6 +2,8 @@
 # between master..seen, are there merges that bring in 
 # more than one topic at a time?
 
+export LANG=C LC_ALL=C
+
 endpoint=${1-seen}
 
 cnt1=$(git lgf --grep="Merge branch '" master..$endpoint | wc -l)