streamclone: define first iteration of version 2 of stream format
(This patch is based on a first draft from Gregory Szorc, with deeper rework)
Version 1 of the stream clone format was invented many years ago and suffers
from a few deficiencies:
1) Filenames are stored in store-encoded (on filesystem) form rather than in
their internal form. This makes future compatibility with new store
filename encodings more difficult.
2) File entry "headers" consist of a newline of the file name followed by the
string file size. Converting strings to integers is avoidable overhead. We
can't store filenames with newlines (manifests have this limitation as
well, so it isn't a major concern). But the big concern here is the
necessity for readline(). Scanning for newlines means reading ahead and
that means extra buffer allocations and slicing (in Python) and this makes
performance suffer.
3) Filenames aren't compressed optimally. Filenames should be compressed well
since there is a lot of repeated data. However, since they are scattered
all over the stream (with revlog data in between), they typically fall
outside the window size of the compressor and don't compress.
4) It can only exchange stored based content, being able to exchange caches
too would be nice.
5) It is limited to a stream-based protocol and isn't suitable for an on-disk
format for general repository reading because the offset of individual file
entries requires scanning the entire file to find file records.
As part of enabling streaming clones to work in bundle2, #2 proved to have a
significant negative impact on performance. Since bundle2 provides the
opportunity to start fresh, Gregory Szorc figured he would take the
opportunity to invent a new streaming clone data format.
The new format devised in this series addresses #1, #2, and #4. It punts on #3
because it was complex without yielding a significant gain and on #5 because
devising a new store format that "packs" multiple revlogs into a single
"packed revlog" is massive scope bloat. However, this v2 format might be
suitable for streaming into a "packed revlog" with minimal processing. If it
works, great. If not, we can always invent stream format when it is needed.
This patch only introduces the bases of the format. We'll get it usable through
bundle2 first, then we'll extend the format in future patches to bring it to its
full potential (especially #4).
$ . "$TESTDIR/histedit-helpers.sh"
$ cat >> $HGRCPATH <<EOF
> [extensions]
> histedit=
> EOF
$ modwithdate ()
> {
> echo $1 > $1
> hg ci -m $1 -d "$2 0"
> }
$ initrepo ()
> {
> hg init $1
> cd $1
> for x in a b c d e f ; do
> echo $x$x$x$x$x > $x
> hg add $x
> done
> hg ci -m 'Initial commit'
> modwithdate a 1
> modwithdate b 2
> modwithdate c 3
> modwithdate d 4
> modwithdate e 5
> modwithdate f 6
> echo 'I can haz no commute' > e
> hg ci -m 'does not commute with e' -d '7 0'
> cd ..
> }
$ initrepo r
$ cd r
Initial generation of the command files
$ EDITED="$TESTTMP/editedhistory"
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 3 >> $EDITED
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 4 >> $EDITED
$ hg log --template 'fold {node|short} {rev} {desc}\n' -r 7 >> $EDITED
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 5 >> $EDITED
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 6 >> $EDITED
$ cat $EDITED
pick 092e4ce14829 3 c
pick ae78f4c9d74f 4 d
fold 42abbb61bede 7 does not commute with e
pick 7f3755409b00 5 e
pick dd184f2faeb0 6 f
log before edit
$ hg log --graph
@ changeset: 7:42abbb61bede
| tag: tip
| user: test
| date: Thu Jan 01 00:00:07 1970 +0000
| summary: does not commute with e
|
o changeset: 6:dd184f2faeb0
| user: test
| date: Thu Jan 01 00:00:06 1970 +0000
| summary: f
|
o changeset: 5:7f3755409b00
| user: test
| date: Thu Jan 01 00:00:05 1970 +0000
| summary: e
|
o changeset: 4:ae78f4c9d74f
| user: test
| date: Thu Jan 01 00:00:04 1970 +0000
| summary: d
|
o changeset: 3:092e4ce14829
| user: test
| date: Thu Jan 01 00:00:03 1970 +0000
| summary: c
|
o changeset: 2:40ccdd8beb95
| user: test
| date: Thu Jan 01 00:00:02 1970 +0000
| summary: b
|
o changeset: 1:cd997a145b29
| user: test
| date: Thu Jan 01 00:00:01 1970 +0000
| summary: a
|
o changeset: 0:1715188a53c7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Initial commit
edit the history
$ hg histedit 3 --commands $EDITED 2>&1 | fixbundle
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
merging e
warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
Fix up the change (fold 42abbb61bede)
(hg histedit --continue to resume)
fix up
$ echo 'I can haz no commute' > e
$ hg resolve --mark e
(no more unresolved files)
continue: hg histedit --continue
$ HGEDITOR=cat hg histedit --continue 2>&1 | fixbundle | grep -v '2 files removed'
d
***
does not commute with e
HG: Enter commit message. Lines beginning with 'HG:' are removed.
HG: Leave message empty to abort commit.
HG: --
HG: user: test
HG: branch 'default'
HG: changed d
HG: changed e
merging e
warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
Fix up the change (pick 7f3755409b00)
(hg histedit --continue to resume)
just continue this time
keep the non-commuting change, and thus the pending change will be dropped
$ hg revert -r 'p1()' e
$ hg resolve --mark e
(no more unresolved files)
continue: hg histedit --continue
$ hg diff
$ hg histedit --continue 2>&1 | fixbundle
7f3755409b00: skipping changeset (no changes)
log after edit
$ hg log --graph
@ changeset: 5:1300355b1a54
| tag: tip
| user: test
| date: Thu Jan 01 00:00:06 1970 +0000
| summary: f
|
o changeset: 4:e2ac33269083
| user: test
| date: Thu Jan 01 00:00:07 1970 +0000
| summary: d
|
o changeset: 3:092e4ce14829
| user: test
| date: Thu Jan 01 00:00:03 1970 +0000
| summary: c
|
o changeset: 2:40ccdd8beb95
| user: test
| date: Thu Jan 01 00:00:02 1970 +0000
| summary: b
|
o changeset: 1:cd997a145b29
| user: test
| date: Thu Jan 01 00:00:01 1970 +0000
| summary: a
|
o changeset: 0:1715188a53c7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Initial commit
contents of e
$ hg cat e
I can haz no commute
manifest
$ hg manifest
a
b
c
d
e
f
$ cd ..
Repeat test using "roll", not "fold". "roll" folds in changes but drops message and date
$ initrepo r2
$ cd r2
Initial generation of the command files
$ EDITED="$TESTTMP/editedhistory.2"
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 3 >> $EDITED
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 4 >> $EDITED
$ hg log --template 'roll {node|short} {rev} {desc}\n' -r 7 >> $EDITED
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 5 >> $EDITED
$ hg log --template 'pick {node|short} {rev} {desc}\n' -r 6 >> $EDITED
$ cat $EDITED
pick 092e4ce14829 3 c
pick ae78f4c9d74f 4 d
roll 42abbb61bede 7 does not commute with e
pick 7f3755409b00 5 e
pick dd184f2faeb0 6 f
log before edit
$ hg log --graph
@ changeset: 7:42abbb61bede
| tag: tip
| user: test
| date: Thu Jan 01 00:00:07 1970 +0000
| summary: does not commute with e
|
o changeset: 6:dd184f2faeb0
| user: test
| date: Thu Jan 01 00:00:06 1970 +0000
| summary: f
|
o changeset: 5:7f3755409b00
| user: test
| date: Thu Jan 01 00:00:05 1970 +0000
| summary: e
|
o changeset: 4:ae78f4c9d74f
| user: test
| date: Thu Jan 01 00:00:04 1970 +0000
| summary: d
|
o changeset: 3:092e4ce14829
| user: test
| date: Thu Jan 01 00:00:03 1970 +0000
| summary: c
|
o changeset: 2:40ccdd8beb95
| user: test
| date: Thu Jan 01 00:00:02 1970 +0000
| summary: b
|
o changeset: 1:cd997a145b29
| user: test
| date: Thu Jan 01 00:00:01 1970 +0000
| summary: a
|
o changeset: 0:1715188a53c7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Initial commit
edit the history
$ hg histedit 3 --commands $EDITED 2>&1 | fixbundle
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
merging e
warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
Fix up the change (roll 42abbb61bede)
(hg histedit --continue to resume)
fix up
$ echo 'I can haz no commute' > e
$ hg resolve --mark e
(no more unresolved files)
continue: hg histedit --continue
$ hg histedit --continue 2>&1 | fixbundle | grep -v '2 files removed'
merging e
warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
Fix up the change (pick 7f3755409b00)
(hg histedit --continue to resume)
just continue this time
$ hg revert -r 'p1()' e
$ hg resolve --mark e
(no more unresolved files)
continue: hg histedit --continue
$ hg histedit --continue 2>&1 | fixbundle
7f3755409b00: skipping changeset (no changes)
log after edit
$ hg log --graph
@ changeset: 5:b538bcb461be
| tag: tip
| user: test
| date: Thu Jan 01 00:00:06 1970 +0000
| summary: f
|
o changeset: 4:317e37cb6d66
| user: test
| date: Thu Jan 01 00:00:04 1970 +0000
| summary: d
|
o changeset: 3:092e4ce14829
| user: test
| date: Thu Jan 01 00:00:03 1970 +0000
| summary: c
|
o changeset: 2:40ccdd8beb95
| user: test
| date: Thu Jan 01 00:00:02 1970 +0000
| summary: b
|
o changeset: 1:cd997a145b29
| user: test
| date: Thu Jan 01 00:00:01 1970 +0000
| summary: a
|
o changeset: 0:1715188a53c7
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Initial commit
contents of e
$ hg cat e
I can haz no commute
manifest
$ hg manifest
a
b
c
d
e
f
description is taken from rollup target commit
$ hg log --debug --rev 4
changeset: 4:317e37cb6d66c1c84628c00e5bf4c8c292831951
phase: draft
parent: 3:092e4ce14829f4974399ce4316d59f64ef0b6725
parent: -1:0000000000000000000000000000000000000000
manifest: 4:b068a323d969f22af1296ec6a5ea9384cef437ac
user: test
date: Thu Jan 01 00:00:04 1970 +0000
files: d e
extra: branch=default
extra: histedit_source=ae78f4c9d74ffa4b6cb5045001c303fe9204e890,42abbb61bede6f4366fa1e74a664343e5d558a70
description:
d
done with repo r2
$ cd ..