git mailsplit

Pre-step for git am on a big mailbox.

🎯 What & why

Splits a single mbox file (or a stream of concatenated emails) into one file per message, numbered 0001, 0002, etc. The git am workflow's first stage when feeding a big mailbox.

🧠 Mental model

Input: an mbox. Output: a directory of single-message files with zero-padded sequence numbers. That's it - no parsing, no patch extraction; that's mailinfo's job.

🛠️ Synopsis

git mailsplit -o<dir> [-b] [-d<prec>] [-f<nr>] [--keep-cr] [--mboxrd]
              [<mbox>|<dir>...]

# Typical use: explode a downloaded mbox
git mailsplit -o./patches inbox.mbox

# Result:
./patches/0001
./patches/0002
./patches/0003
...

🎚️ Switches & options

Flag	What it does
`-o<dir>`	Output directory (must exist); files are written here
`-b`	Treat any file that isn't an mbox as a single bare email
`-d<n>`	Use n-digit zero-padded numbers (default 4: `0001`)
`-f<n>`	Start numbering at n instead of 1
`--keep-cr`	Preserve CRLF line endings instead of normalizing to LF
`--mboxrd`	Parse as mboxrd format (handles `>From` un-escaping correctly)

💡 Use cases

Apply a maintainer's mbox: git mailsplit -o./p mbox && git am ./p/*.
Renumber a second batch starting after the first: -f5.
Convert a directory of .eml files into a uniformly numbered set.
Preserve CRLF when patches contain Windows line endings that matter (--keep-cr).

🧪 Examples

Split an mbox

mkdir patches && git mailsplit -o./patches inbox.mbox

Custom width and start

git mailsplit -o./p -d3 -f10 inbox.mbox   # 010, 011, ...

Single bare email

git mailsplit -b -o./p single.eml

Then apply with am

git am ./patches/*

🎓 Recommendations

Create the output dir first; mailsplit doesn't mkdir -p.
Use --mboxrd if your mbox came from a tool that escapes >From ; otherwise messages can be silently truncated.
Combine with git am --keep-cr if you used --keep-cr here, for symmetric handling.

🪤 Common pitfalls

Default mbox parsing splits on bare From lines, which can break inside quoted text - --mboxrd is safer.
Output filenames have no extension - shell globs like *.eml won't match.
Existing files in the output dir aren't cleared; you can end up mixing old and new batches.

🔗 Related modules

📝 Quiz

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