Git log to JSON without hand-rolled escaping

The direct conversion

Run this inside a repository. --no-decorate keeps branch and tag labels out of the commit hash field; jc-rs reads the standard commit blocks and writes one JSON object per commit.

git log -n 20 --no-decorate |
  jc-rs --git-log > commits.json

A default record includes the full commit hash, author name and email, the displayed date, the complete commit message, and parsed epoch fields. Empty author names and email addresses remain null instead of disappearing.

You can also use jc-rs magic syntax: jc-rs git log -n 20 --no-decorate. The explicit pipe is easier to extend with Git options and makes the data boundary obvious in a script.

Why JSON-shaped pretty formats are brittle

A common shortcut asks Git to print text that resembles a JSON object:

git log --format='{"commit":"%H","subject":"%s"}'

Git substitutes the subject directly into that template. A subject containing a double quote, backslash, tab, or control character needs JSON escaping that the format string does not provide. Multi-line bodies add another delimiter problem, and joining the objects into an array introduces comma handling.

git log --no-decorate |
  jc-rs --git-log |
  jq 'map({commit, author, date, message})'

Use a Git format the parser understands

The parser covers Git's familiar log styles and stat blocks. Choose the least verbose style that contains the fields you need.

git log -n 10 --format=fuller --no-decorate |
  jc-rs --git-log |
  jq 'map({commit, author, commit_by, date, commit_by_date})'

Avoid arbitrary custom --format strings here. The parser needs recognizable commit, identity, date, message, and stat lines; it cannot infer the meaning of an unrelated delimiter scheme.

Practical Git log to JSON recipes

A compact release-note feed

git log v1.4.0..HEAD --no-merges --no-decorate |
  jc-rs --git-log |
  jq 'map({
    commit: .commit[0:12],
    author,
    subject: (.message | split("\n")[0])
  })'

Commit counts by author

git log --since='2026-01-01' --no-decorate |
  jc-rs --git-log |
  jq 'group_by(.author)
    | map({author: .[0].author, commits: length})
    | sort_by(-.commits)'

Changed-line totals from stat output

git log -n 50 --stat --no-decorate |
  jc-rs --git-log |
  jq 'map({
    commit: .commit[0:12],
    files: (.stats.files_changed // 0),
    lines: ((.stats.insertions // 0) + (.stats.deletions // 0))
  })'

Only commits touching one path

git log --no-decorate -- website/src/ |
  jc-rs --git-log |
  jq 'map({commit, author, message})'

Let Git perform revision, merge, author, date, and path selection. It can walk its own graph more efficiently than jq can filter an unnecessarily large history afterward.

Treat an empty history and a failed command separately

An empty revision range is valid and becomes an empty JSON array. A bad revision or a failed parser is an error. Bash needs pipefail to preserve failures from the left side of the pipeline; jq can enforce a non-empty result when the job requires one.

#!/usr/bin/env bash
set -Eeuo pipefail

range=${1:-HEAD~10..HEAD}

if ! git log "$range" --no-decorate |
  jc-rs --git-log |
  jq -e '
    if length > 0
    then map({commit, author, message})
    else error("revision range contains no commits")
    end
  ' >commits.json
then
  printf 'could not build commit report for %s\n' "$range" >&2
  exit 1
fi

The range is passed to Git as one quoted argument. It is never interpolated into the jq program.

Boundaries worth knowing

• This parses log text, not the Git object database. Git remains responsible for revision walking, path filters, mailmap behavior, and date selection.
• Disable decorations for stable hashes. Branch and tag labels are presentation text; keep them out of the commit field unless they are intentionally part of your report.
• Oneline input needs full hashes. Add --no-abbrev-commit. The abbreviated form is not enough for the parser's oneline record boundary.
• Large histories are batch output. The regular Git parser returns one array after input ends. Limit the range in Git rather than converting years of history for a ten-commit report.