git mailinfo

Used by git am internally.

🎯 What & why

Parses a single email patch (the kind git format-patch produces) into a clean message + diff. It's the lower-level tool that git am uses internally.

🧠 Mental model

Input: one email (mbox-ish). Output: a cleaned commit message on stdout plus a separate patch file. Headers like From:, Subject:, Date: are extracted into a key-value info file.

🛠️ Synopsis

git mailinfo [-k|-b] [-u|--encoding=<enc>|-n] [--[no-]scissors] [--quoted-cr=<action>]
             <msg> <patch>

# Reads RFC822 email from stdin, writes:
#   <msg>   - cleaned commit message body
#   <patch> - the diff portion
# stdout:   - "Author: ...", "Email: ...", "Subject: ...", "Date: ..."

cat 0001-fix.patch | git mailinfo msg.out patch.out

🎚️ Switches & options

Flag	What it does
`-k`	Keep subject as-is; don't strip `[PATCH]`/`Re:` prefixes
`-b`	Like -k but only keep `[bracketed]` strings that aren't `[PATCH]`
`-u`	Re-encode commit message to UTF-8 (default)
`-n`	Disable charset re-encoding entirely
`-m`	Copy the message ID into a `Message-Id:` trailer
`--scissors`	Cut everything before a `>8` scissors line; useful when reviewers paste discussion above the patch
`--no-scissors`	Disable scissors handling (the default)

💡 Use cases

Building a custom mbox -> commit pipeline that diverges from what git am does.
Inspecting how git will parse a tricky multi-part email before running git am.
Salvaging a patch from an email where the subject has been mangled (-k).
Stripping reviewer chatter above a -- >8 -- scissors line.

🧪 Examples

Basic split

git mailinfo msg patch < 0001-fix.patch

Keep raw subject

git mailinfo -k msg patch < weird-subject.eml

Honor scissors line

git mailinfo --scissors msg patch < review-thread.eml

No re-encoding

git mailinfo -n msg patch < latin1.eml

🎓 Recommendations

If you just want to apply a patch email, use git am - mailinfo is for when you need to inspect or transform the pieces.
Always check both output files; the patch file is empty if the email had no diff.
Pair with git mailsplit for mboxes with many messages.

🪤 Common pitfalls

mailinfo overwrites <msg> and <patch> without warning - watch your filenames.
MIME multi-part messages with attachments can confuse the parser; pre-flatten to text/plain.
Without -k, the [PATCH v3 1/4] prefix gets stripped, which is usually what you want but surprising if you're capturing it.

🔗 Related modules

📝 Quiz

Hit each option, then Check answers. Score is recorded; Next is always open.