Environment variables affect

The Role of Environment Variables in Git

Environment variables are dynamic values used by the operating system or applications during runtime, and Git also relies on them to control its behavior. These variables can configure Git's default paths, proxy settings, editor choices, and more. For example, GIT_DIR specifies the location of the .git directory, and GIT_EDITOR determines the text editor used for interactive operations.

# Temporarily set the editor for Git commits
export GIT_EDITOR="code --wait"
git commit  # This will open the commit message in VSCode

Core Environment Variables Explained

Repository-Related Variables

GIT_DIR overrides the default .git directory location, which is particularly useful when managing multiple worktrees. When executing git init, Git will create the repository structure at this path instead of the current directory.

# Initialize a repository in a non-standard location
export GIT_DIR="/config/project.git"
git init

GIT_WORK_TREE specifies the working directory. When used with GIT_DIR, it enables separation between bare repositories and working areas:

export GIT_DIR="/repo.git"
export GIT_WORK_TREE="/project/src"
git status  # Check the file status in /src

Identity Authentication Variables

GIT_AUTHOR_NAME and GIT_AUTHOR_EMAIL override the globally configured user information. This is useful when distinguishing between personal and work commits:

// Temporarily set author information in a Node.js script
process.env.GIT_AUTHOR_NAME = 'CI Bot';
process.env.GIT_AUTHOR_EMAIL = 'ci@example.com';
require('child_process').execSync('git commit -m "Build"');

Network and Proxy Configuration

GIT_HTTP_PROXY and GIT_HTTPS_PROXY control the proxy servers used for HTTP(S) protocols, taking precedence over system proxy settings. Useful for bypassing corporate firewalls:

export GIT_HTTPS_PROXY="http://proxy.internal:3128"
git clone https://github.com/org/repo.git

GIT_SSL_NO_VERIFY skips SSL certificate verification (use with caution), suitable for testing environments:

export GIT_SSL_NO_VERIFY="1"
git push  # Ignores certificate errors

Debugging and Log Control

GIT_TRACE outputs detailed runtime trace information, helping diagnose connection issues:

export GIT_TRACE=1
git fetch  # Displays detailed logs, including protocol packets

GIT_CURL_VERBOSE logs all raw HTTP communication data:

export GIT_CURL_VERBOSE=1
git clone http://example.com/repo.git

Cross-Platform Differences

Windows systems require attention to environment variable naming differences. For example, setting the SSH command path:

# Set the SSH executable in PowerShell
$env:GIT_SSH = "C:\Program Files\PuTTY\plink.exe"

On Linux/macOS, use the standard path format:

export GIT_SSH="/usr/local/bin/ssh"

Environment Variables in Hooks

Git hook scripts can access special variables. For example, GIT_INDEX_FILE points to the staging area index file:

#!/bin/sh
# Check the index path in a pre-commit hook
echo "Staging area: $GIT_INDEX_FILE"

GIT_REFLOG_ACTION contains a description of the operation being performed:

# Get the action type in a post-commit hook
import os
print(f"Action: {os.getenv('GIT_REFLOG_ACTION')}")

Variable Priority and Scope

Environment variables take precedence over gitconfig settings. For example, when both a global email and an environment variable are set:

git config --global user.email "personal@example.com"
export GIT_AUTHOR_EMAIL="work@company.com"
# The actual commit will use work@company.com

In terms of scope, some variables only affect specific commands. For example, GIT_MERGE_VERBOSITY only adjusts the log level for merge operations:

export GIT_MERGE_VERBOSITY=5
git merge feature  # Outputs detailed merge decision process

Practical Tips and Pitfalls

For persistent settings, it's recommended to write them to shell configuration files rather than global gitconfig. For example, add the following to .zshrc:

# Distinguish work project identity
function git-work() {
  export GIT_AUTHOR_EMAIL="work@company.com"
  export GIT_COMMITTER_EMAIL=$GIT_AUTHOR_EMAIL
}

Common mistakes include misspelling variable names, causing them to not take effect. For example, incorrectly setting GIT_EDITER instead of GIT_EDITOR.