revisionbranchcache: fall back to slow path if starting readonly (issue4531)
Transitioning to Mercurial versions with revision branch cache could be slow as
long as all operations were readonly (revset queries) and the cache would be
populated but not written back.
Instead, fall back to using the consistently slow path when readonly and the
cache doesn't exist yet. That avoids the overhead of populating the cache
without writing it back.
If not readonly, it will still populate all missing entries initially. That
avoids repeated writing of the cache file with small updates, and it also makes
sure a fully populated cache available for the readonly operations.
# A B
#
# 3 4 3
# |\/| |\
# |/\| | \
# 1 2 1 2
# \ / \ /
# 0 0
#
# if the result of the merge of 1 and 2
# is the same in 3 and 4, no new manifest
# will be created and the manifest group
# will be empty during the pull
#
# (plus we test a failure where outgoing
# wrongly reported the number of csets)
$ hg init a
$ cd a
$ touch init
$ hg ci -A -m 0
adding init
$ touch x y
$ hg ci -A -m 1
adding x
adding y
$ hg update 0
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ touch x y
$ hg ci -A -m 2
adding x
adding y
created new head
$ hg merge 1
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -A -m m1
$ hg update -C 1
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg merge 2
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -A -m m2
created new head
$ cd ..
$ hg clone -r 3 a b
adding changesets
adding manifests
adding file changes
added 4 changesets with 3 changes to 3 files
updating to branch default
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg clone -r 4 a c
adding changesets
adding manifests
adding file changes
added 4 changesets with 3 changes to 3 files
updating to branch default
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg -R a outgoing b
comparing with b
searching for changes
changeset: 4:1ec3c74fc0e0
tag: tip
parent: 1:79f9e10cd04e
parent: 2:8e1bb01c1a24
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: m2
$ hg -R a outgoing c
comparing with c
searching for changes
changeset: 3:d15a0c284984
parent: 2:8e1bb01c1a24
parent: 1:79f9e10cd04e
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: m1
$ hg -R b outgoing c
comparing with c
searching for changes
changeset: 3:d15a0c284984
tag: tip
parent: 2:8e1bb01c1a24
parent: 1:79f9e10cd04e
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: m1
$ hg -R c outgoing b
comparing with b
searching for changes
changeset: 3:1ec3c74fc0e0
tag: tip
parent: 1:79f9e10cd04e
parent: 2:8e1bb01c1a24
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: m2
$ hg -R b pull a
pulling from a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg -R c pull a
pulling from a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)