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gfix

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Amend a git commit further back in the history.

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How to use this skill

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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/ryanb/dotfiles/blob/HEAD/claude/skills/gfix/SKILL.md

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First, summarize what it does, its dependencies, license status if identifiable, and any risks. Show the exact files you propose to add under .agents/skills/gfix/. Do not write files or run scripts until I approve.

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Copying this prompt does not install or run the skill. Review third-party files before use. Codex skill guide

gfix — Amend a Past Commit

Use the gfix shell command to fold staged changes into a commit that is not the most recent. This is the preferred way to amend historical commits in this repo.

MUST use gfix. When this skill is loaded, every modification to a past commit goes through the gfix command. Do not reach for git rebase -i, hand-crafted fixup!/amend! commits, or GIT_SEQUENCE_EDITOR=true git rebase --autosquash directly — gfix already does all of this, with stash/restore guarantees and conflict handling.

How gfix works

Source: ~/code/dotfiles/plugins/git.zsh (the gfix function)

gfix [-m <message>] <commit-sha> does the following:

  1. Guards against running during an in-progress git operation (rebase, merge, cherry-pick, etc.)
  2. Stashes any unstaged changes (preserving the index)
  3. Creates a fixup commit from whatever is currently staged:
    • With no -m: git commit --fixup <commit-sha> (content-only fixup)
    • With -m <message>: creates a manual amend! commit with subject amend! <original-subject> and body <message>, which autosquash then folds into the target (replacing its message, and including any staged changes; --allow-empty is used if nothing is staged)
  4. Runs GIT_SEQUENCE_EDITOR=true git rebase -i --autosquash <commit-sha>^ to automatically squash the fixup into the target commit
  5. Restores any stashed unstaged changes

When to use gfix

Use gfix when you need to amend a commit that is not the HEAD commit. For example:

  • A review comment asks for a change to code introduced 3 commits ago
  • You notice a typo or bug in an earlier commit while working on something else
  • You want to keep a clean, logical commit history where each commit is self-contained

If you only need to amend the most recent commit, use git commit --amend instead.

Steps

  1. Determine the safe range — The target commit must be within the current branch's own commits, not on or before the base branch. Find the base branch via the tracked parent in git config branch.$(git branch --show-current).parent, falling back to bin/base-branch if that script exists. As a last resort, ask the user.

    The target commit must appear in git log --oneline <base-branch>..HEAD. If it does not, stop and tell the user — rewriting shared history would cause problems.

  2. Identify the target commit — Use $ARGUMENTS to understand what the user wants fixed. List the safe commits with git log --oneline <base-branch>..HEAD and examine their diffs to find the commit that introduced the code the user wants changed.

  3. Make and stage the changes — Edit the files, then git add only the files that belong to the target commit.

  4. Run gfix — Pass the target commit SHA. Add -m <message> to also rewrite the target commit's message:

    gfix <commit-sha>
gfix -m "new commit message" <commit-sha>

  5. Handle rebase conflicts — If the rebase hits conflicts:

    • Read the conflicting files and resolve them
    • git add the resolved files
    • git rebase --continue
    • Repeat until the rebase finishes

  6. Verify — Run git log --oneline -10 to confirm the history looks correct. If relevant tests exist, run them.