go-git - Commit Timestamp

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This is related to the previous post, Git Commit Signature Verification. That post was based on the work of implementing git commit signature verification in src-d/go-git. This post is a sequel to that in a way.

The previous post ended with an example of how to create a custom commit and run verification on it.

ts := time.Unix(0000000000, 0)
commit := &Commit{
    Hash:      plumbing.NewHash("8a9cea36fe052711fbc42b86e1f99a4fa0065deb"),
    Author:    Signature{Name: "darkowlzz", Email: "example@darkowlzz.space", When: ts},
    Committer: Signature{Name: "darkowlzz", Email: "example@darkowlzz.space", When: ts},
    Message: `status: simplify template command selection

The problem here is that the timestamp being added to the commit has no location attached to it. Hence, it uses the local timezone of the machine where it runs. Due to this, the test started failing when run on machines in different timezones.

The signature that was generated was against a fixed timezone and the above code would change the commit timezone everytime it runs depending on the location of the machine.

Git commits are written with timestamps containing the timezone of the machine. Once written, it’s not regenerated or changed by normal reading operations.

commit 13df556177b33fcfe1187343bd54837e48ec0b52
Merge: 9d269a6 770a444
Author: -------------------------
Date:   Mon Nov 20 13:28:18 2017 -0500

A fix for the above issue would be to add a fixed location to the created timestamp.

loc, _ := time.LoadLocation("Asia/Tokyo")
    Author:    Signature{Name: "darkowlzz", Email: "example@darkowlzz.space", When: ts.In(loc)},

That would ensure that the timestamp is always the same in that commit.

The previous post had a note about signature verification failure due to an invisible newline at the end of commit message, this post highlights another reason for the verification to fail, timestamp.

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