---
name: git-history

description: >
  Use when investigating git history — pickaxe (`-S`/`-G`) or `-L` line-range log
  queries, tracing when a change landed, bisecting what broke something, or
  locating a commit to revert or backport. Not authoring or rebasing commits ->
  `git-commits`. Not a Gitea server's history -> `gitea-branches`.

metadata:
  version: "1.0.1"
  category: git
  source_keys:
    - git-scm-bisect-docs
    - git-scm-log-docs
    - git-scm-diff-docs

allowed-tools: Bash
---

## Gotchas

- `-S"string"` matches only where the string's *count* changed, so a line edited in place matches `-G"regex"` and not `-S`. Reach for `-G` whenever the string may have moved rather than appeared.
- `--follow` traces renames for exactly one path. Given several paths or a glob it fails instead of degrading, so run it once per file.
- Under `git bisect run`, exit `128` or above **aborts the session** rather than marking the commit bad, so a crashing test script ends the search silently.
- Bisect answering "cannot find exact culprit" beside skipped commits is a complete result: it is as precise as the skip range allows.

## Step 1 — Pick the entry procedure

| What is known | Procedure |
|---|---|
| Content, a file, or a line range to search for | Query the log — Step 2 |
| Nothing to search for — only that the behaviour changed between two points | Bisect — read `references/bisect.md` |
| The commit itself, already identified | Step 3 |

## Step 2 — Query the log

Default to `rtk git log --oneline`, then narrow by whatever is known:

- **Content**: `rtk git log -S"string"`, or `-G"regex"` to match any diff line. `--pickaxe-regex` makes the `-S` argument a POSIX ERE; `--pickaxe-all` shows every file in a matching changeset.
- **A line or function**: `git log -L <start>,<end>:<file>` or `git log -L :<function>:<file>` — bare, not `rtk`: rtk truncates each diff line at ~72 characters (ADR-0023). Confirm the range resolves before reporting on it — an off-by-one silently omits the target.
- **A file across renames**: `rtk git log --follow -- <file>`. Without `--follow` the history stops at the rename boundary.
- **Mainline only**: `--first-parent` follows the integration branch and skips commits merged in from side branches.
- **Structured output**: `rtk git log --format="%h | %s | %an (%ar)"`.

If you need the placeholder catalogue, format presets, `--diff-filter` letters, full `-L` syntax, ancestry filters, pickaxe binary-file behaviour, or `git diff` output-control flags such as `--stat`, `--word-diff` and the whitespace options, read `references/git-log-format.md`.

## Step 3 — Act on a located commit

Offer the operation and its consequence; run it only once the user has chosen.

- Backporting the commit to another branch is a cherry-pick, and cherry-pick is `git-commits`' — it owns the destination-branch check, the `rtk git` wrapper and the `--abort` path. Hand it the SHA; do not run `git cherry-pick` from here.
- `rtk git revert <commit>` adds a new commit undoing it — for un-applying merged work without rewriting history.
- `rtk git blame <file>` attributes each line to the commit that last touched it, when the question is which commit introduced one specific line.

For diff output control on the located commit, read `references/git-log-format.md`.

## Step 4 — Return the result

Report each located commit in this shape, so a calling agent can act on it without reparsing raw log output:

```text
<sha> — <subject>
<author> (<relative date>)
Recommendation: <action or "none">
```