## Overview

`revgrep` is a CLI tool used to filter static analysis tools to only lines changed based on a commit reference.

## Install

```bash
go install github.com/golangci/revgrep/cmd/revgrep@latest
```

## Usage

In the scenario below, a change was made causing a warning in `go vet` on line 5, but `go vet` will show all warnings.
Using `revgrep`, you can show only warnings for lines of code that have been changed (in this case, hiding line 6).

```bash
[user@host dir (master)]$ go vet
main.go:5: missing argument for Sprintf("%s"): format reads arg 1, have only 0 args
main.go:6: missing argument for Sprintf("%s"): format reads arg 1, have only 0 args
[user@host dir (master)]$ go vet |& revgrep
main.go:5: missing argument for Sprintf("%s"): format reads arg 1, have only 0 args
```

`|&` is shown above as many static analysis programs write to `stderr`, not `stdout`, `|&` combines both `stderr` and
`stdout`. It could also be achieved with `go vet 2>&1 | revgrep`.

`revgrep` CLI tool will return an exit status of 1 if any issues match, else it will return 0. Consider using
`${PIPESTATUS[0]}` for the exit status of the `go vet` command in the above example.

```
Usage: revgrep [options] [from-rev] [to-rev]

from-rev filters issues to lines changed since (and including) this revision
  to-rev filters issues to lines changed since (and including) this revision, requires <from-rev>

  If no revisions are given, and there are unstaged changes or untracked files, only those changes are shown
  If no revisions are given, and there are no unstaged changes or untracked files, only changes in HEAD~ are shown
  If from-rev is given and to-rev is not, only changes between from-rev and HEAD are shown.

    -d    Show debug output
      -regexp string
              Regexp to match path, line number, optional column number, and message
```

## Other Examples

Issues between branches:
```bash
[user@host dir (feature/branch)]$ go vet |& revgrep master
```

Issues since last push:
```bash
[user@host dir (master)]$ go vet |& revgrep origin/master
```
