branchcache: add a "pure topological head" fast path
In a narrow but actually quick common case, all topological heads are all on
the same branch and all open. In this case, computing the branch map is very
simple. We can quickly detect situation where this situation will not change.
So we update the V3 format to be able to express this situation and upgrade the
update code to detect we remains in that mode.
The branch cache is populated with the actual value when the branch map is
accessed, but the update_disk method can do the update without needing to
populate it.
A script that implements uppercasing all letters in a file.
$ UPPERCASEPY="$TESTTMP/uppercase.py"
$ cat > $UPPERCASEPY <<EOF
> import sys
> from mercurial.utils.procutil import setbinary
> setbinary(sys.stdin)
> setbinary(sys.stdout)
> sys.stdout.write(sys.stdin.read().upper())
> EOF
$ TESTLINES="foo\nbar\nbaz\n"
$ printf $TESTLINES | "$PYTHON" $UPPERCASEPY
FOO
BAR
BAZ
This file attempts to test our workarounds for pickle's lack of
support for short reads.
$ cat >> $HGRCPATH <<EOF
> [extensions]
> fix =
> [fix]
> uppercase-whole-file:command="$PYTHON" $UPPERCASEPY
> uppercase-whole-file:pattern=set:**
> EOF
$ hg init repo
$ cd repo
# Create a file that's large enough that it seems to not fit in
# pickle's buffer, making it use the code path that expects our
# _blockingreader's read() method to return bytes.
$ echo "some stuff" > file
$ for i in $($TESTDIR/seq.py 13); do
> cat file file > tmp
> mv -f tmp file
> done
$ hg commit -Am "add large file"
adding file
Check that we don't get a crash
$ hg fix -r .
saved backup bundle to $TESTTMP/repo/.hg/strip-backup/*-fix.hg (glob)