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CHANGESET EVOLUTION Boris Feld June 22, 2017 octobus.net

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LET'S GET STARTED

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ONCE UPON A TIME

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YOU FIX A BUG (With a small typo) Parent Fx bug

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YOU WRITE MORE CODE

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URGENT MERGE

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FIX THE FIX But it's easy to fix them: Parent Fix bug hg commit --amend -m "Fix bug"

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TOO FAST! But wait you had local changes! And they get incorporated into the amend. 10 more minutes to unbundle revert the files, relaunch the tests, etc...

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WITH EVOLVE NOW Parent Fx bug

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SAME CLI With evolve this time: Parent Fix bug hg commit --amend -m "Fix bug"

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OK WHAT THE DIFFERENCE?

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BEFORE / AFTER Before: After: $> hg log -G -T compact @ 1 0abbeece133b Fix bug | o 0 5e5cd613e43b ROOT $> hg log -G -T compact @ 2 b1739dd137e5 Fix bug | o 0 5e5cd613e43b ROOT

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DIFFERENCE IS HIDDEN The old revision is still there! $> hg log -G -T compact --hidden o 2 b1739dd137e5 Fix bug | | x 1 6b2be349e073 Fx bug |/ o 0 5e5cd613e43b ROOT

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IMPACT Easier to access obsolete changesets No more .hg/strip-backup/ expedition Respect the append only model of Mercurial No large data movement on edition No cache trauma

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ONE MORE THING

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TRACK EVOLUTION Parent Fix bug Fx bug

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OBSMARKER Stores relation between evolutions Successor Predecessor And some metas: User Date And others...

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STACK WORKFLOW

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STACK $> hg stack ### topic: myfeature ### branch: feature t4@ Step4 (current) t3: Step3 t2: Step2 t1: Step ^ Trunk

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WHY STACK? Feature = multiple steps, Smaller = Simpler Simpler = Earlier merge in trunk Ease experiment with Alternative etc…

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PREV $> hg prev 1 files updated, 0 files merged, 0 files removed, 0 files unresolved [7] Step3 $> hg stack ### topic: myfeature ### branch: feature t4: Step4 t3@ Step3 (current) t2: Step2 t1: Step ^ Trunk

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NEXT $> hg next 1 files updated, 0 files merged, 0 files removed, 0 files unresolved [8] Step4 $> hg stack ### topic: myfeature ### branch: feature t4@ Step4 (current) t3: Step3 t2: Step2 t1: Step ^ Trunk

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T# $> hg update --rev t2 1 files updated, 0 files merged, 0 files removed, 0 files unresolved [8] Step4 $> hg stack ### topic: myfeature ### branch: feature t4: Step4 t3: Step3 t2@ Step2 (current) t1: Step ^ Trunk

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EDITING MID-STACK $> hg update --rev t1 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $> hg commit --amend -m "Step1" 3 new unstable changesets

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WHAT HAVE WE DONE? $> hg log -G -T compact @ 9[tip] 1aa1be5ada40 Step1 | | o 8 cf90b2de7e65 Step4 (unstable) | | | o 7 e208d4205c8e Step3 (unstable) | | | o 6 673ff300cf3a Step2 (unstable) | | | x 5 8bb88a31dd28 Step |/ o 4 3294c1730df7 Trunk ~

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STACK TO THE RESCUE! $> hg stack ### topic: myfeature ### branch: feature t4$ Step4 (unstable) t3$ Step3 (unstable) t2$ Step2 (unstable) t1@ Step1 (current) ^ Trunk

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DON'T PANIC $> hg next --evolve move:[6] Step2 atop:[9] Step1 working directory now at d72473cbf9a6 $> hg stack ### topic: myfeature ### branch: feature t4$ Step4 (unstable) t3$ Step3 (unstable) t2@ Step2 (current) t1: Step1 ^ Trunk

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GO ON

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GO ON $> hg next --evolve move:[7] Step3 atop:[10] Step2 working directory now at 4062d6ecd214 $> hg stack ### topic: myfeature ### branch: feature t4$ Step4 (unstable) t3@ Step3 (current) t2: Step2 t1: Step1 ^ Trunk

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GO ON $> hg next --evolve move:[8] Step4 atop:[11] Step3 working directory now at 4dcd9dfedf1b $> hg stack ### topic: myfeature ### branch: feature t4@ Step4 (current) t3: Step3 t2: Step2 t1: Step1 ^ Trunk

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GO ON $> hg next --evolve no children

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BETTER! $> hg log -G -T compact @ 12[tip] 4dcd9dfedf1b Step4 | o 11 4062d6ecd214 Step3 | o 10 d72473cbf9a6 Step2 | o 9 1aa1be5ada40 Step1 | o 4 3294c1730df7 Trunk ~

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MORE REWRITE TOOLS Operation command Modify hg amend Remove hg prune Move hg grab Split hg split Fold hg fold

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MULTI HEADED STACK $> hg stack ### topic: myfeature (2 heads) ### branch: feature t6@ Step 4.5 (current) t4^ Step4 (base) t5: Step 5 t4: Step4 t3: Step3 t2: Step2 t1: Step1 ^ Trunk

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DISTRIBUTED WORKFLOW

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PROPAGATION Obsolescence can be exchanged: push, pull bundle / unbundle (hg 4.3+) (affects draft history only)

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EXCHANGING DRAFT Works on multiple machines Collaborate with others Whole new play field == new traps

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EXAMPLE Root A Root A

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TIME PASS Root A1 A Root A B

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INSTABILITY Root A1 A B

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IT'S SMART

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STABILIZATION Root A1 A B1 B

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REWRITE ANYTHING? Phases enforce a reliable history: draft: can we rewritten public: immutable part of the history Contact your local workflow manager.

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HELPFULL TOOLING

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SUMMARY $> hg summary parent: 10:890ac95deb83 tip (unstable) Head branch: feature commit: (clean) update: (current) phases: 9 draft unstable: 1 changesets topic: myfeature

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LOG $ hg log -G --hidden -T '{node|short}\n{obsfate}\n' @ c55cb2ee8a91 | o 23abfc79b7ce | | o 4302274177b9 (unstable) | | | x fba593aaaa10 |/ rewritten as c55cb2ee8a91; o 2ff53d8bf7d7

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EVOLVE --LIST (see also hg evolve --list --rev) $> hg evolve --list 9ac0d376e01c: changelog: introduce a 'tiprev' method unstable: 52ec3072fe46 (obsolete parent) 3efd3eab9860: changelog: use 'tiprev()' in 'tip()' unstable: 9ac0d376e01c (unstable parent)

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OBSLOG $> hg obslog @ c55cb2ee8a91 (4) A2 | | o 4302274177b9 (2) A1 |/ x fba593aaaa10 (1) A rewritten(description, parent) as c55cb2ee8a91 by Boris Feld (Thu Jun 22 00:00:29 2017 +0200) rewritten(description) as 4302274177b9 by Boris Feld (Thu Jun 22 00:00:28 2017 +0200)

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OBSLOG --PATCH $> hg obslog -p @ f6b1dded9e95 (2) A1 | x 364e589e2bac (1) A rewritten(description, parent) as a6be771bedcf by Boris Feld (Thu Jun 22 00:00:29 2017 +0200) (No patch available yet, changesets rebased) rewritten(description) as f6b1dded9e95 by Boris Feld (Thu Jun 22 00:00:28 2017 +0200) --- a/364e589e2bac-changeset-description +++ b/f6b1dded9e95-changeset-description @@ -1,1 +1,1 @@ -A +A1

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JOURNAL $> hg journal previous locations of '.': 2fb6d364d453 commit --amend -m Step1 701fb5d73e07 update --rev t1 ae11635effb7 commit -A -m Step2 701fb5d73e07 commit -A -m Step

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SEMANTIC

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USE THE RIGHT COMMANDS!

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SMART COMMANDS Operation command Modify hg amend Remove hg prune Move hg grab Split hg split Fold hg flog

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TROUBLES

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EVOLUTION Unlock powerful unique features Hide most of the complexity Help with unstable situations Automatic detection Automated resolution hg help evolve

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INSTABILITY (currently: troubles) Orphans: ancestors were rewritten Divergence: branching in evolutions Content-divergence: independent rewrites Phase-divergence: older version got published

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CONCLUSION

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WORK IN PROGRESS Concepts are solid Implementation in progress Common case works fine Some rough edges Feedback → priority

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USE EVOLUTION TODAY install hg-evolve [extensions] evolve= topic= # provides hg stack

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HELPS Slack: #devs-mercurial-evolve Mailing-list: [email protected] IRC channel: #mercurial

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DOCUMENTATION Documentation: Wiki: https://www.mercurial-scm.org/doc/evolution/index.html https://www.mercurial-scm.org/wiki/EvolveExtension

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CONCLUSION

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REWRITE ALL THE THINGS!

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SAFETY FIRST!

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EXTRA - TROUBLES

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OBSOLETE Root New Obsolete

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UNSTABLE Now called orphan Root New Obsolete Unstable

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BUMPED Now called Phase-divergent Root New Obsolete Bumped

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DIVERGENT Now called Content-divergent Root Base Divergent1 Divergent2

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EXTRA-COMMANDS

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AMEND Root A To amend A: Root A1 A hg amend -m 'A1'

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PRUNE Root A To prune A: Root A hg prune -r "desc(A)"

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REBASE Root B A In order to rebase A on top of B; Root B A A' hg rebase -r "desc(A)" -d "desc(B)"

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FOLD Root A B To fold A and B: Root C A B hg fold -r "desc(A)" -r "desc(B)" -m "C"

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SPLIT Root A Split in two: Root B A C hg split -r "desc(A)"

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