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.
$ cat > writepatterns.py <<EOF
> import sys
>
> path = sys.argv[1]
> patterns = sys.argv[2:]
>
> fp = open(path, 'wb')
> for pattern in patterns:
> count = int(pattern[0:-1])
> char = pattern[-1].encode('utf8') + b'\n'
> fp.write(char * count)
> fp.close()
> EOF
prepare repo
$ hg init a
$ cd a
These initial lines of Xs were not in the original file used to generate
the patch. So all the patch hunks need to be applied to a constant offset
within this file. If the offset isn't tracked then the hunks can be
applied to the wrong lines of this file.
$ "$PYTHON" ../writepatterns.py a 34X 10A 1B 10A 1C 10A 1B 10A 1D 10A 1B 10A 1E 10A 1B 10A
$ hg commit -Am adda
adding a
This is a cleaner patch generated via diff
In this case it reproduces the problem when
the output of hg export does not
import patch
$ hg import -v -m 'b' -d '2 0' - <<EOF
> --- a/a 2009-12-08 19:26:17.000000000 -0800
> +++ b/a 2009-12-08 19:26:17.000000000 -0800
> @@ -9,7 +9,7 @@
> A
> A
> B
> -A
> +a
> A
> A
> A
> @@ -53,7 +53,7 @@
> A
> A
> B
> -A
> +a
> A
> A
> A
> @@ -75,7 +75,7 @@
> A
> A
> B
> -A
> +a
> A
> A
> A
> EOF
applying patch from stdin
patching file a
Hunk #1 succeeded at 43 (offset 34 lines).
Hunk #2 succeeded at 87 (offset 34 lines).
Hunk #3 succeeded at 109 (offset 34 lines).
committing files:
a
committing manifest
committing changelog
created 189885cecb41
compare imported changes against reference file
$ "$PYTHON" ../writepatterns.py aref 34X 10A 1B 1a 9A 1C 10A 1B 10A 1D 10A 1B 1a 9A 1E 10A 1B 1a 9A
$ diff aref a
$ cd ..