rust: add Vfs trait
This will allow for the use of multiple vfs like in the Python implementation,
as well as hiding the details of the upcoming Python vfs wrapper to hg-core.
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Check that we can compute and exchange revision rank properly
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$ cat << EOF >> $HGRCPATH
> [format]
> exp-use-changelog-v2=enable-unstable-format-and-corrupt-my-data
> EOF
Test minimal rank computation with merge
$ hg init rank-repo-minimal
$ cd rank-repo-minimal
$ touch 0
$ hg commit -Aqm 0
$ touch 1
$ hg commit -Aqm 1
$ hg update -qr 0
$ touch 2
$ hg commit -Aqm 2
$ hg merge -qr 1
$ hg commit -m 3
$ touch 4
$ hg commit -Aqm 4
$ hg log --graph --template '{rev} {_fast_rank}\n'
@ 4 5
|
o 3 4
|\
| o 2 2
| |
o | 1 2
|/
o 0 1
$ cd ..
Build a bigger example repo
$ hg init rank-repo-generated
$ cd rank-repo-generated
$ hg debugbuilddag '.:root1+5:mp1<root1+10:mp2/mp1+3<mp1+2:mp3/mp2$+15/mp1+4'
$ hg log -G -T '{desc}'
o r42
|
o r41
|
o r40
|
o r39
|
o r38
|\
| o r37
| |
| o r36
| |
| o r35
| |
| o r34
| |
| o r33
| |
| o r32
| |
| o r31
| |
| o r30
| |
| o r29
| |
| o r28
| |
| o r27
| |
| o r26
| |
| o r25
| |
| o r24
| |
| o r23
|
| o r22
| |\
| | o r21
| | |
+---o r20
| |
| | o r19
| | |
| | o r18
| | |
| | o r17
| | |
+---o r16
| |/
| o r15
| |
| o r14
| |
| o r13
| |
| o r12
| |
| o r11
| |
| o r10
| |
| o r9
| |
| o r8
| |
| o r7
| |
| o r6
| |
o | r5
| |
o | r4
| |
o | r3
| |
o | r2
| |
o | r1
|/
o r0
Check the rank
--------------
$ hg log -G -T '{_fast_rank}'
o 26
|
o 25
|
o 24
|
o 23
|
o 22
|\
| o 15
| |
| o 14
| |
| o 13
| |
| o 12
| |
| o 11
| |
| o 10
| |
| o 9
| |
| o 8
| |
| o 7
| |
| o 6
| |
| o 5
| |
| o 4
| |
| o 3
| |
| o 2
| |
| o 1
|
| o 19
| |\
| | o 8
| | |
+---o 7
| |
| | o 20
| | |
| | o 19
| | |
| | o 18
| | |
+---o 17
| |/
| o 11
| |
| o 10
| |
| o 9
| |
| o 8
| |
| o 7
| |
| o 6
| |
| o 5
| |
| o 4
| |
| o 3
| |
| o 2
| |
o | 6
| |
o | 5
| |
o | 4
| |
o | 3
| |
o | 2
|/
o 1