This document provides details on E3SM development conventions and practices.
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important -- Items colored in red mean they are important, and should not be ignored.
one time -- Items colored in green are commands to be issued once per machine.
repo once -- Items colored in orange are commands to be issued once per local repository.
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While working on a feature or a bug fix, you will be editing source code files. After editing a file, you might want to commit those changes to your local repository in order to checkpoint your work, or track the change you made. By default, git doesn’t track any files in the repository unless they are explicitly added to the repository. In order to add a file to the repository, you can use the following . When you make a change that you want to commit you "add" it to the git stage with this command:
git add path/to/file/in/repo
In addition to causing git to track the file, this will also stage all changes in the file. The next commit that is created will contain all changes in the stage by default. If you create a new file, also use git add to make the repo aware of it.
A commit can have changes from multiple files. In order to commit only the changes in the staging area, the following command can be used:
git commit
NOTE: The git add command will only stage the changes in the file at the time you issue the command. If the file is subsequently modified you need to run git add again if you want those changes to be committed. Use git status frequently to see the status of staged and un-staged files.
git commit will open up an editor where a commit message can be written. Please refer to the Commit and PR message template for more instructions on the E3SM commit message guidelines.
It is tempting to do development with lots of little commits like this:
f8ef2b5f75 fix
d2e3616d55 progress
e58c74745f more progress
0be335ead0 almost working
If you make "checkpoint" commits like this, be prepared to rewrite the commit history using "git rebase" (See https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History) so that each commit has a substantive message as required in Commit and PR message template. See
Utilizing the repository history
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Your PR is not finished until it has been merged to master by the Integrator.
This document can be used to help with pull request related issues.
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- Check the github entry for the PR and make sure it has a good title and description, correct labels and a comment with a link to the Design Document. A PR can not be merged to next or master unless it has a Design Document with Phase 1 and 2 completed. See /wiki/spaces/CNCL/pages/25231511.
- Look at the code changes either on github or using: git log --reverse -p master.. on your checked out copy of the branch.
- Does new code hold up to visual inspection for code quality? Look over code changes for glaring mistakes or code style issues (e.g. useful comments, reasonable subroutine lengths, new code in an existing file follows conventions of that file).
- Check to see if the description of the code changes in the PR match the actual changes. Make sure nothing unrelated to the PR was committed accidentally.
- Although they can't be changed, see if commit messages on the branch follow the Commit and PR message template and let the developer know if they can not. Consider asking the developer to squash commits to clean up the history.
- Have tests been added or suggested that exercise this feature?
- Does code run on all platforms after integration into next?
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Before communicating with remotes, you might want to add or remove remotes. In order to add and remove remotes the git remote command can be used. The two uses are as follows:
git remote add remote-name protocol:address/to/repo # Creates a remote
git remote remove remote-name # Removes a remote
In order to communicate with remotes, there are three actions. push, pull, and fetch.
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- "frequent pulling of the \[master] into a development branch will add a certain amount of randomness to that branch; this randomness is not particularly helpful for somebody who is trying to get a feature working. It also increases the chances that another developer who ends up in the middle of the series while running a bisect operation will encounter unrelated bugs."
- A branch has a specific purpose. A topic branch 'add-frotz' would be about adding a new 'frotz' feature and shouldn't do anything else. When you merge from master, you declare that all the other unrelated changes done on 'master' in preparation for the next release somehow bring 'add-frotz' closer to the goal of the 'frotz' topic. That is usually not true
- Unnecessary merges and similar repository clutter reduces the ability to summarize, audit, notice bugs in review, and find bugs after the fact. Keeping clean history is not difficult. It requires a little bit of discipline on the part of integrators and developers, but it's a small price to pay for the time saved and improved quality/reliability.
There are some cases where merging from master (or better, a tagged version of master) can make sense. The rule of thumb for any merge is that if you can clearly describe what you are merging and why that merge is necessary for your branch to be completed, then it's fine to merge. For example, you might need a feature on master (some crucial functionality, not just a build system updates) to complete the feature on your branch. Integrators may ask you to merge from master to help resolve conflicts during a PR integration. But before merging from master, try one of the other ways to get features from other peoples development described in Incorporatinganotherbranchontoyourbranch.
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