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.
This test cover a bug that no longer exist.
Define helpers.
$ hg_log () { hg log -G -T "{rev}:{node|short}"; }
$ commit () { echo "foo - ${2:-$1}" > $1; hg commit -Aqm "Edited $1"; }
$ strip() { hg --config extensions.strip= strip -q -r "$1" ; }
Setup hg repo.
$ hg init repo
$ cd repo
$ touch x; hg add x; hg commit -m "initial"
$ hg clone -q . ../clone
$ commit a
$ cd ../clone
$ commit b
$ hg pull -q ../repo
$ ls -1 .hg/cache/branch?*
.hg/cache/branch2-base
.hg/cache/branch2-served
$ cat .hg/cache/branch?-served
222ae9789a75703f9836e44de7db179cbfd420ee 2
a3498d6e39376d2456425dd8c692367bdbf00fa2 o default
222ae9789a75703f9836e44de7db179cbfd420ee o default
$ hg_log
o 2:222ae9789a75
|
| @ 1:a3498d6e3937
|/
o 0:7ab0a3bd758a
$ strip '1:'
After the strip the "served" cache is now identical to the "base" one, and the
older one have been actively deleted.
$ ls -1 .hg/cache/branch?*
.hg/cache/branch2-base
$ cat .hg/cache/branch?-base
7ab0a3bd758a58b9f79557ce708533e627776cce 0
7ab0a3bd758a58b9f79557ce708533e627776cce o default
We do a new commit and we get a new valid branchmap for the served version
$ commit c
$ ls -1 .hg/cache/branch?*
.hg/cache/branch2-base
.hg/cache/branch2-served
$ cat .hg/cache/branch?-served
a1602b357cfca067600406eb19060c7128804d72 1
a1602b357cfca067600406eb19060c7128804d72 o default
On pull we end up with the same tip, and so wrongly reuse the invalid cache and crash.
$ hg pull ../repo --quiet
$ hg heads -T '{rev} {node} {branch}\n'
2 222ae9789a75703f9836e44de7db179cbfd420ee default
1 a1602b357cfca067600406eb19060c7128804d72 default
$ ls -1 .hg/cache/branch?*
.hg/cache/branch2-base
.hg/cache/branch2-served
$ cat .hg/cache/branch?-served
222ae9789a75703f9836e44de7db179cbfd420ee 2
a1602b357cfca067600406eb19060c7128804d72 o default
222ae9789a75703f9836e44de7db179cbfd420ee o default