Version Control

Solve

• Older Generations

  • SVN, Perforce, CVS …

• Alternative

  • Git, Mercurial, Pujil, Plastic SCM

Why ?

• technical constraints,

• Features,

• new usages,

• diversity.

Mono-Repo

• Gather all code in a single repository,

• Common repository but separated project,

• Simplified collaboration.

Mono-Repo: Advantages

• Simplification
  • Dependency
  • Standardisation
  • Tooling
  • Discovery

Mono-Repo: Advantages

• Atomic Changes
  • Consistent state
  • Refactoring,
  • Continuous Integration.

Mono-Repo: Drawback

• increased:

  • number of file,
  • history size,
  • storage and bandwidth,
  • server load.

• access control

Solution: Narrow Clone

• restricted to file needed,

• reduce:

  • number of file,
  • storage and bandwidth,
  • history,

• access control,

Solution: Narrow Clone

• Full access still available

  • cross projects teams,
  • tooling and testing.

Narrow Clone: example

Non-Source File

• binaries
• test data,
• media,
• etc

Different File

• few ability to diff,
• larges,
• hard to store,

Options?

• artifact manager,
• build system,
• source control,

git-LFS

• From Github,
• extensible format,
• standard network protocol,
• (better) supported by Mercurial

LFS: example

Growing history

• more and more changes,
• project grow,
• team grow,

Client and Server Load

• spread load between multiple server
  • redundancy,
  • scaling,
• caching,
  • less processing,
  • network locality,
• storage sharing,

Improving algorithm

• Eg: Idea from SCCS (1972)
  • git annotate js/src/jsapi.cpp
    • 9.951s
  • hg annotate js/src/jsapi.cpp
    • 7.690s
  • hg fastannotate js/src/jsapi.cpp
    • 0.360s

Strong Integration

• kernel collaboration
• dedicated file system,
  • Google,
  • Facebook,
  • Microsoft,
  • …

Strong Integration

• user actions through other tools,
  • Github,
  • Gitlab,
  • Mozilla
  • …

Development Process

• new good practices
  • tests
  • code review
  • automatic formatting
  • … ?
• impact on VCS?

Auto Formatting

• clearer source
• standard format:
  • Go
  • Rust
  • C/C++ (eg: Clang)
  • Python (eg: pep8/black)

Source of Friction

• global and deep,
• evolving,
  • configuration,
  • version,

Solution?

• Working with the VCS

Code Review

• catch bug,
• share skills,
• spread code ownership,
• review your own code!

Stacked Approach

• Series of atomic and clear changes,
• progressive integration,
• involve VCS and associated tooling
  • finer creation
  • finer update
  • etc…

Example

Collaborative Platform

• code review,
• continuous integration,
• workflow merge, deployment
• “classic” (ticket, wiki, etc)

Heptapod

• effort toward Gitlab + Mercurial
• working Prototype
• come chat with us
• https://heptapod.net

Closer Collaboration

• dependant branches
• intra-branch collaboration
• exchanging draft
• collaborative rewriting

Changeset Evolution

• Exclusive feature of Mercurial
• safe and simple distributed rewriting
• help:
  • collaboration,
  • review,

Changeset Evolution demonstration

Conclusion

• lots interesting issues
• lots of solutions
• future will be surprise-full
• Mercurial is well armed to the future
• long live free software alternatives

Questions

• https://octobus.net
• email: contact@octobus.net
• IRC: #octobus-hg
• https://mercurial-scm.org