使用 GPG 签名 Git Commits

$ gpg --gen-key
gpg (GnuPG/MacGPG2) 2.0.28; Copyright (C) 2015 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Please select what kind of key you want:
   (1) RSA and RSA (default)
   (2) DSA and Elgamal
   (3) DSA (sign only)
   (4) RSA (sign only)
Your selection?
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048)
Requested keysize is 2048 bits
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 1y
Key expires at 日  6/11 22:33:50 2017 CST
Is this correct? (y/N) y

GnuPG needs to construct a user ID to identify your key.

Real name: xxx
Email address: xxx@yyy.com
Comment:
You selected this USER-ID:
    "xxx <xxx@yyy.com>"

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit?
Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
You need a Passphrase to protect your secret key.

We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
gpg: key B5DB6617 marked as ultimately trusted
public and secret key created and signed.

gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0  valid:   3  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 3u
gpg: next trustdb check due at 2017-06-11
pub   2048R/B5DB6617 2016-06-11 [expires: 2017-06-11]
      Key fingerprint = 3AE5 19D5 8A58 C59B B029  6CEA 8566 6A47 B5DB 6617
uid       [ultimate] xxx <xxx@yyy.com>
sub   2048R/1F4A9B85 2016-06-11 [expires: 2017-06-11]

git config commit.gpgsign true

$ git config --global commit.gpgsign true

$ git commit -S -m "comment"

$ git ci -m "test"
gpg: skipped "ZZZ <xxx@yyy.com>": No secret key
gpg: signing failed: No secret key
error: gpg failed to sign the data
fatal: failed to write commit object

$ git add .
$ git ci -m "test"

You need a passphrase to unlock the secret key for
user: "xxx <xxx@yyy.com>"
4096-bit RSA key, ID C0B176D7, created 2016-06-11

[master (root-commit) 163d909] test
 1 file changed, 3 insertions(+)
 create mode 100644 README.md

$ gpg --list-secret-keys
/Users/xxx/.gnupg/secring.gpg
-------------------------------
sec   4096R/C0B176D7 2016-06-11 [expires: 2020-06-11]
uid                  xxx <xxx@yyy.com>
ssb   4096R/E00F263F 2016-06-11

$ gpg --armor --export C0B176D7
-----BEGIN PGP PUBLIC KEY BLOCK-----
Comment: GPGTools - https://gpgtools.org

****************************************************************
****************************************************************
****************************************************************
************************************************
*****
-----END PGP PUBLIC KEY BLOCK-----