absorb: preserve changesets which were already empty
Most commands in Mercurial (commit, rebase, absorb itself) don’t create empty
changesets or drop them if they become empty. If there’s a changeset that’s
empty, it must be a deliberate choice of the user. At least it shouldn’t be
absorb’s responsibility to prune them. The fact that changesets that became
empty during absorb are pruned, is unaffected by this.
This case was found while writing patches which make it possible to configure
absorb and rebase to not drop empty changesets. Even without having such config
set, I think it’s valuable to preserve changesets which were already empty.
$ hg init
$ 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