branchcache: skip entries that are topological heads in the on disk file
In the majority of cases, topological heads are also branch heads. We have
efficient way to get the topological heads and efficient way to retrieve
their branch information. So there is little value in putting them in the branch
cache file explicitly. On the contrary, writing them explicitly tend to create
very large cache file that are inefficient to read and update.
So the branch cache v3 format is no longer including them. This changeset focus
on the format aspect and have no focus on the performance aspect. We will cover
that later.
$ hg init repo
$ cd repo
$ touch a
$ hg add a
$ hg commit -m "Added a"
$ touch main
$ hg add main
$ hg commit -m "Added main"
$ hg checkout 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
'main' should be gone:
$ ls -A
.hg
a
$ touch side1
$ hg add side1
$ hg commit -m "Added side1"
created new head
$ touch side2
$ hg add side2
$ hg commit -m "Added side2"
$ hg log
changeset: 3:91ebc10ed028
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added side2
changeset: 2:b932d7dbb1e1
parent: 0:c2eda428b523
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added side1
changeset: 1:71a760306caf
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added main
changeset: 0:c2eda428b523
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added a
$ hg heads
changeset: 3:91ebc10ed028
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added side2
changeset: 1:71a760306caf
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added main
$ ls -A
.hg
a
side1
side2
$ hg update --debug -C 1
resolving manifests
branchmerge: False, force: True, partial: False
ancestor: 91ebc10ed028+, local: 91ebc10ed028+, remote: 71a760306caf
side1: other deleted -> r
removing side1
side2: other deleted -> r
removing side2
main: remote created -> g
getting main
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ ls -A
.hg
a
main