3. What is DVCS?
Distributed revision control system
or
Distributed version control system
or
Decentralized version control system
or, simply
the greatest thing since sliced bread?
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4. What is Version Control?
• Belongs to Software Configuration Management
• Management of changes (over time) to
• Documents
• Source code
• Web sites (and any other collections of information)
1.0
2.0
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3.0
file a
file b
file c
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5. Traditional VCS
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• Centralized
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• Client-server approach
• Single point of failure
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Server
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• Most operations require
network connection
• Support for locking
resources
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6. DVCS
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• Peer-to-peer, based on
the exchange of patches
• Collaboration without
common network
• Every working copy is a
standalone repository
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CI
QA
Rel.
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8. Terms
Repository
A container of assets, e.g. source code. Commonly a directory in a filesystem
containing
special meta-data about the repository contents (.git and .hg directories).
Working directory
The repository contents editable in the filesystem.
Commit, changeset
A change applied to the repository contents (multiple files at one) within a
transaction.
Given a unique identified (a hash code).
Patch
A set of commits (one or more) transferred between repositories.
Clone
A full copy of another (upstream) repository. The initial copying operation
of a repository
into another is called cloning.
Push
Making changesets from the local repository (source) available in another
(destination).
Pull
Making changesets from an external repository available locally.
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14. Isolation
Work on new, great ideas now, share the results later
appel
ttcopley
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15. Disadvantages
• Cloning retrieves everything
• Uses a lot of bandwidth on the first clone
• Might use a lot of disk space as well
• Problematic for non-mergeable content
• No support for locking
• Locking can be useful for non-mergeable content
• Non-mergeable content?
• For example, graphics assets, i.e. large binary files
• Always stored in full, for every change
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16. Everything is a Branch
• Working copies
• Named branches
• Release branches
• Deployment targets
• Light-weight branches
• Feature branches
• Bug fix branches
• Exploratory branches
• Multiple heads in a repository
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FeatheredTar
(Mercurial)
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17. Branching Model
• Everybody should know:
• When to branch; where to
branch from
• When to merge; where to
merge back to
• Tailor the model for your
environment
• Heavy vs. light
• Common model
• Git Flow
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http://nvie.com/posts/a-successful-git-branching-model/
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20. Steps for Feature Branching
1. Fork a new branch for each individual change
2. Work on and test the branch in isolation
3. Pull changes from the mother branch
continuously (keep up-to-date with others)
4. When ready, publish the changes by creating a
pull request
• Let others review the pull request for quality control
5. Merge the accepted pull request back to the
upstream branch (mother branch)
6. Get rid of the (short-lived) feature branch
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21. Pull requests
• Clear point for reviews and quality control
• Checklists, formal reviews, performance testing
• Final merge can be done by an integrator (role)
• Multiple features/fixes developed in parallel
• Efficiency
• Isolation until final merge
• Mainline can maintain high level of quality at all times
• No need to delay work due to release preparation
• Release from mainline at will
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31. Images from Flickr
Images Creative Commons-licensed for commercial use
http://creativecommons.org/licenses/by-sa/2.0/legalcode
(The image owners’ Flickr URL attached to each image as a
hyperlink)
Screenshots from Atlassian
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Operations on a large repositories do not suffer from latency.Performance has been a key factor during the design of DVCS tools.Things happen almost instantly.Helps people to stay in the flow.Encourages small, regular and frequent commits.NOPEUS
