parsers: fix width of datalen variable in fm1readmarkers
Because parsers.c does not define PY_SSIZE_T_CLEAN, "s#" format requires
(const char*, int), not (const char*, Py_ssize_t).
https://docs.python.org/2/c-api/arg.html
This error had no problem before 042344313939, where datalen wasn't used.
But now fm1readmarkers() fails with "overflow in obsstore" on Python 2.6.9
(amd64) because upper bits of datalen seem to be filled with 1, making it
a negative integer.
This problem seems not visible on our Python 2.7 environment because upper
bits happen to be filled with 0.
Issue1678: IndexError when pushing
setting up base repo
$ hg init a
$ cd a
$ touch a
$ hg ci -Am a
adding a
$ cd ..
cloning base repo
$ hg clone a b
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd b
setting up cset to push
$ hg up null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ touch a
different msg so we get a clog new entry
$ hg ci -Am b
adding a
created new head
pushing
$ hg push -f ../a
pushing to ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
$ cd ..