shelve: make shelvestate use simplekeyvaluefile
Currently shelvestate uses line ordering to differentiate fields. This
makes it hard for extensions to wrap shelve, since if two alternative
versions of code add a new line, correct merging is going to be problematic.
simplekeyvaluefile was introduced fot this purpose specifically.
After this patch:
- shelve will always write a simplekeyvaluefile
- unshelve will check the first line of the file for a version, and if the
version is 1, will read it in a position-based way, if the version is 2,
will read it in a key-value way
As discussed with Yuya previously, this will be able to handle old-style
shelvedstate files, but old Mercurial versions will fail on the attempt to
read shelvedstate file of version 2 with a self-explanatory message:
'abort: this version of shelve is incompatible with the version used
in this repo'
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ echo b > b
$ hg ci -Am1
adding b
$ hg tag -r0 default
warning: tag default conflicts with existing branch name
$ hg log
changeset: 2:30a83d1e4a1e
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added tag default for changeset f7b1eb17ad24
changeset: 1:925d80f479bb
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 1
changeset: 0:f7b1eb17ad24
tag: default
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
$ hg update 'tag(default)'
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg parents
changeset: 0:f7b1eb17ad24
tag: default
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
$ hg update 'branch(default)'
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg parents
changeset: 2:30a83d1e4a1e
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Added tag default for changeset f7b1eb17ad24
$ cd ..