git-status-snap

git-status-snap is a utility implemented in Crystal that runs and parses git status to constituent shell environment variables that can be sourced by a Bash, Zsh or Fish script to render a fast Git-aware prompt.

Many custom prompts directly run and parse git status using shell commands. However, parsing the output of git status using shell commands is much slower than doing the same using optimized Crystal, often twice as slow depending on the size of the repository.

Note, this utility is used to accelerate the bash-seafly-prompt.

Installation

Copy, and untar, the appropriate git-status-snap binary, from Releases, to somewhere in the current $PATH.

Alternatively, if the Crystal build chain is available, clone this repository and build a release via make and copy the git-status-snap binary from bin/git-status-snap to somewhere in the current $PATH.

Requirements

Git version 2.11, released in November 2016, or later is required.

Usage

In your prompt script source the output of git_status_snap to evaluate the current Git state.

In Bash or Zsh that would look as follows:

. <(git-status-snap)

And in Fish:

git-status-snap | source

Note, if using Fish just as an interactive shell, as opposed to a login shell, please make sure that the SHELL environment variable is set to your running version of the fish executable (for example /bin/fish).

Here is an example usage of git-status-snap in a very simple Bash prompt script:

_my_prompt() {
    . <(git-status-snap)

    if [[ -n $GSF_REPOSITORY ]]; then
        PS1="\w $GSF_BRANCH> "
    else
        PS1="\w> "
    fi
}

PROMPT_COMMAND=_my_prompt

Refer to the bash-seafly-prompt command script for a real-world usage of git-status-snap.

Implementation

git-status-snap will run the following git status command in the current working directory:

git --no-optional-locks status --porcelain=v2 --branch --show-stash --ignore-submodules -uno

The result from that git status command will internally be parsed and transformed to a series of shell environment variable statements, ready for sourcing from a custom prompt script.

The relevant environment variables, using the GSF prefix (short for Git Status Flag), will be:

GSF_UPSTREAM values:

• 0 Current and remote branches are equal

• 1 Current branch is ahead of remote tracking branch

• -1 Current branch is behind remote tracking branch

• 2 Current and remote branches have diverged

Note, the absence of any environment variable indicates falsehood, for example if GSF_REPOSITORY is unset then that signals the current directory is not a Git repository.

For performance reasons, untracked files and change counts are ignored.

Recommendations

Very large repositories, such as the Linux kernel and the Chromium browser, will result in slow git status execution.

For such repositories, it is strongly recommended to enable the following configuration options directly in those very large repositories:

• git config feature.manyFiles true will adopt internal Git settings to improve performance for large repositories as documented here

• git config core.fsmonitor true will enable Git file system monitor as documented here

Note, as of May 2023 fsmonitor is only available for Windows and macOS.

License