discovery-helper: use reflink copy if available
A reflink copy will copy the files "as usual" but keep using the same data block
underneath. This is only supported by "copy on write" file system like btrfs or
zfs.
This will achieve similar performance that the existing hardlink clone that
Mercurial performs with the same initial space saving. However, it will behave
better on revlogs start being touch by strip. Instead of duplicating all data in
the touched revlogs, only the block actually affected by the strip will be
duplicated. This save a lot of space when building many variants of large
repositories.
The --reflink=always flag make sure the `cp` call fails if reflink copies are
not supported. Falling back to local clone.
# 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
new changesets 5fcb73622933:d15a0c284984
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
new changesets 5fcb73622933:1ec3c74fc0e0
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)
new changesets 1ec3c74fc0e0
(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)
new changesets d15a0c284984
(run 'hg heads' to see heads, 'hg merge' to merge)