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How to write an arbitrary blob to a repository to add “supplemental” information, such as contact information or your public GPG key, but without making that blob part of the standard history.

The recipe

Feed arbitrary text into git hash-object, and write the corresponding blob to the object store:

echo "Robert P. J. Day" | git hash-object -w --stdin
$ git show 8a1385ff5d6ab8c195f99931042b7afaf418e6b0
Robert P. J. Day

In order for that blob not to be garbage-collected, tag it:

$ git tag fullname 8a1385ff5d6ab8c195f99931042b7afaf418e6b0

Show it:

$ git show fullname
Robert P. J. Day

In fact, this technique is used by Git maintainer Junio Hamano to disseminate his public GPG key with the Git source code:

$ git show junio-gpg-pub
tag junio-gpg-pub
Tagger: Junio C Hamano <>
Date:   Thu Nov 20 15:12:15 2014 -0800

GPG key to sign git.git archive

This blob contains the GPG public key I use to sign git.git archive.

To use it to verify tags I signed, do:

  $ git-cat-file blob junio-gpg-pub | gpg --import

to import it into your keyring, and then

  $ git-tag -v $tag_to_be_verified

The fingerprint information for the key is as follows:

$ gpg --fingerprint -k 96AFE6CB\!
pub   4096R/713660A7 2011-10-01
      Key fingerprint = 96E0 7AF2 5771 9559 80DA  D100 20D0 4E5A
      7136 60A7
uid                  Junio C Hamano <>
uid                  Junio C Hamano <>
uid                  Junio C Hamano <>
sub   4096R/833262C4 2011-10-01
sub   4096R/96AFE6CB 2011-10-03 [expires: 2015-09-21]
sub   4096R/B3F7CAC9 2014-09-20 [expires: 2017-09-19]
Version: GnuPG v1


... etc etc ...
git_writing_an_arbitrary_blob.txt · Last modified: 2019/03/07 10:14 by rpjday