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modularml / stack-pr

A tool for working with stacked PRs on github.
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Stacked PRs for GitHub

This is a command-line tool that helps you create multiple GitHub pull requests (PRs) all at once, with a stacked order of dependencies.

Imagine that we have a change A and a change B depending on A, and we would like to get them both reviewed. Without stacked PRs one would have to create two PRs: A and A+B. The second PR would be difficult to review as it includes all the changes simultaneously. With stacked PRs the first PR will have only the change A, and the second PR will only have the change B. With stacked PRs one can group related changes together making them easier to review.

Example: StackedPRExample1

Dependencies

This is a non-comprehensive list of dependencies required by stack-pr.py:

Installation

To install via pipx run:

pipx install stack-pr

Manually, you can clone the repository and run the following command:

pipx install .

Workflow

stack-pr is a tool allowing you to work with stacked PRs: submit, view, and land them.

The stack-pr tool has four commands:

A usual workflow is the following:

while not ready to merge:
    make local changes
    commit to local git repo or amend existing commits
    create or update the stack with `stack-pr.py submit`
merge changes with `stack-pr.py land`

You can also use view at any point to examine the current state, and abandon to drop the stack.

Under the hood the tool creates and maintains branches named $USERNAME/stack/$BRANCH_NUM and embeds stack metadata into commit messages, but you are not supposed to work with those branches or edit that metadata manually. I.e. instead of pushing to these branches you should use submit, instead of deleting them you should use abandon and instead of merging them you should use land.

The tool looks at commits in the range BASE..HEAD and creates a stack of PRs to apply these commits to TARGET. By default, BASE is main (local branch), HEAD is the git revision HEAD, and TARGET is main on remote (i.e. origin/main). These parameters can be changed with options -B, -H, and -T respectively and accept the standard git notation: e.g. one can use -B HEAD~2, to create a stack from the last two commits.

Example

The first step before creating a stack of PRs is to double-check the changes we’re going to post.

By default the tool will look at commits in main..HEAD range and will create a PR for every commit in that range.

For instance, if we have

# git checkout my-feature
# git log -n 4  --format=oneline
**cc932b71c** (**my-feature**)        Optimized navigation algorithms for deep space travel
**3475c898f**                         Fixed zero-gravity coffee spill bug in beverage dispenser
**99c4cd9a7**                         Added warp drive functionality to spaceship engine.
**d2b7bcf87** (**origin/main, main**) Added module for deploying remote space probes

Then the tool will consider the top three commits as changes, for which we’re trying to create a stack.

Pro-tip: a convenient way to see what commits will be considered by default is the following command:

alias githist='git log --abbrev-commit --oneline $(git merge-base origin/main HEAD)^..HEAD'

We can double-check that by running the script with view command - it is always a safe command to run:

# stack-pr view
...
VIEW
**Stack:**
   * **cc932b71** (No PR): Optimized navigation algorithms for deep space travel
   * **3475c898** (No PR): Fixed zero-gravity coffee spill bug in beverage dispenser
   * **99c4cd9a** (No PR): Added warp drive functionality to spaceship engine.
SUCCESS!

If everything looks correct, we can now submit the stack, i.e. create all the corresponding PRs and cross-link them. To do that, we run the tool with submit command:

# stack-pr submit
...
SUCCESS!

The command accepts a couple of options that might be useful, namely:

If the command succeeded, we should see “SUCCESS!” in the end, and we can now run view again to look at the new stack:

# stack-pr view
...
VIEW
**Stack:**
   * **cc932b71** (#439, 'ZolotukhinM/stack/103' -> 'ZolotukhinM/stack/102'): Optimized navigation algorithms for deep space travel
   * **3475c898** (#438, 'ZolotukhinM/stack/102' -> 'ZolotukhinM/stack/101'): Fixed zero-gravity coffee spill bug in beverage dispenser
   * **99c4cd9a** (#437, 'ZolotukhinM/stack/101' -> 'main'): Added warp drive functionality to spaceship engine.
SUCCESS!

We can also go to github and check our PRs there:

StackedPRExample2

If we need to make changes to any of the PRs (e.g. to address the review feedback), we simply amend the desired changes to the appropriate git commits and run submit again. If needed, we can rearrange commits or add new ones.

When we are ready to merge our changes, we use land command.

# stack-pr land
LAND
Stack:
   * cc932b71 (#439, 'ZolotukhinM/stack/103' -> 'ZolotukhinM/stack/102'): Optimized navigation algorithms for deep space travel
   * 3475c898 (#438, 'ZolotukhinM/stack/102' -> 'ZolotukhinM/stack/101'): Fixed zero-gravity coffee spill bug in beverage dispenser
   * 99c4cd9a (#437, 'ZolotukhinM/stack/101' -> 'main'): Added warp drive functionality to spaceship engine.
Landing 99c4cd9a (#437, 'ZolotukhinM/stack/101' -> 'main'): Added warp drive functionality to spaceship engine.
...
Rebasing 3475c898 (#438, 'ZolotukhinM/stack/102' -> 'ZolotukhinM/stack/101'): Fixed zero-gravity coffee spill bug in beverage dispenser
...
Rebasing cc932b71 (#439, 'ZolotukhinM/stack/103' -> 'ZolotukhinM/stack/102'): Optimized navigation algorithms for deep space travel
...
SUCCESS!

This command lands the first PR of the stack and rebases the rest. If we run view command after land we will find the remaining, not yet-landed PRs there:

# stack-pr view
VIEW
**Stack:**
   * **8177f347** (#439, 'ZolotukhinM/stack/103' -> 'ZolotukhinM/stack/102'): Optimized navigation algorithms for deep space travel
   * **35c429c8** (#438, 'ZolotukhinM/stack/102' -> 'main'): Fixed zero-gravity coffee spill bug in beverage dispenser

This way we can land all the PRs from the stack one by one.

Specifying custom commit ranges

The example above used the default commit range - main..HEAD, but you can specify a custom range too. Below are several commonly useful invocations of the script:

# Submit a stack of last 5 commits
stack-pr submit -B HEAD~5

# Use 'origin/main' instead of 'main' as the base for the stack
stack-pr submit -B origin/main

# Do not include last two commits to the stack
stack-pr submit -H HEAD~2

These options work for all script commands (and it’s recommended to first use them with view to double check the result). It is possible to mix and match them too - e.g. one can first submit the stack for the last 5 commits and then land first three of them:

# Inspect what commits will be included HEAD~5..HEAD
stack-pr view -B HEAD~5
# Create a stack from last five commits
stack-pr submit -B HEAD~5

# Inspect what commits will be included into the range HEAD~5..HEAD~2
stack-pr view -B HEAD~5 -H HEAD~2
# Land first three PRs from the stack
stack-pr land -B HEAD~5 -H HEAD~2

Command Line Options Reference

The section is not added yet, contributions are welcome!

Config files

Default values for command line options can be specified via a config file. Path to the config file can be specified via STACKPR_CONFIG envvar, and by default it's assumed to be .stack-pr.cfg in the current folder.

An example of a config file:

[common]
verbose=True
hyperlinks=True
draft=False
keep_body=False
[repo]
remote=origin
target=main
reviewer=GithubHandle1,GithubHandle2
branch_name_template=$USERNAME/$BRANCH