'git' Environment and Overriding Settings

In an environment where it is not possible to save author and committer information permanently, a couple of environment variables can be set to specify this information:

• GIT_AUTHOR_NAME for the author's human-readable name
• GIT_AUTHOR_EMAIL for the author's email address

• GIT_COMMITTER_NAME for the committer's human-readable name
• GIT_COMMITTER_EMAIL for the committer's email address

For example

export GIT_AUTHOR_NAME="Martin Burnicki"
export GIT_AUTHOR_EMAIL="martin.burnicki@burnicki.net"
export GIT_COMMITTER_NAME=${GIT_AUTHOR_NAME}
export GIT_COMMITTER_EMAIL=${GIT_AUTHOR_EMAIL}
git commit -m "My sudo commit"

or for a single command:

GIT_AUTHOR_NAME="Martin Burnicki" GIT_AUTHOR_EMAIL="martin.burnicki@burnicki.net" GIT_COMMITTER_NAME=${GIT_AUTHOR_NAME} GIT_COMMITTER_EMAIL=${GIT_AUTHOR_EMAIL} git commit -m "My sudo commit"

Environment variables can also be used to override commit and author dates. See chapter "Check In An Existing Old File With Its Original Date" for details.

By default, git saves project information in a hidden directory named .git. However, if a project contains files from several git repos, e.g. scripts in /usr/local/bin/ from different repos, it is possible to override the default name .git by some other name, using environment variables, or command line parameters. E.g.:

GIT_DIR=.git-repo-1 gitk &
git --git-dir=.git-repo-1 fetch

git commits distinguish between an Author Date and a Commiter Date. By default both are set to the system date and time which is current when the git commit command is executed.

git log only shows the author date by default:

commit 7590a8c4a730ec889798497db259e91ef701caec
Author: Martin Burnicki <martin.burnicki@burnicki.net>
Date:   Fri Mar 29 12:44:04 2019 +0100

whereas e.g. gitk shows both the author and commiter date:

Author: Martin Burnicki <martin.burnicki@burnicki.net>  2019-03-29 12:44:04
Committer: Martin Burnicki <martin.burnicki@burnicki.net>  2019-03-29 12:44:04

This can be useful e.g. if you have a couple of old versions of a file and want to put them into a git repo to improve future tracking, but want to keep the original, historic dates.

More details and examples can be found in

• Working with dates in Git
  https://alexpeattie.com/blog/working-with-dates-in-git

The –date parameter can be used with the commit command to set the author date to the specified date and time, e.g.:

git commit -m "My commit message." --date="2013.04.01 13:45"

However, the commiter date is still set to the current time.

If both the author date and the commiter date are to be specified, the environment variables GIT_AUTHOR_DATE and GIT_COMMITTER_DATE can be used to specify both dates, e.g.

GIT_AUTHOR_DATE="2013.04.01 13:45" GIT_COMMITTER_DATE="2013.04.01 15:45" git commit -m "My commit message."

sets the dates to specified but different values, while

GIT_AUTHOR_DATE="2013.04.01 13:45" GIT_COMMITTER_DATE="${GIT_AUTHOR_DATE}" git commit -m "My commit message."

sets them both to the same value.

When old files from an existing project are to be imported into a newly created 'git' repo, environment variables can be used to set the commit dates to the original file date, and thus maintain the original file history.

git add -f my-old-file
GIT_AUTHOR_DATE="2016-06-11 16:29:04" GIT_COMMITTER_DATE="${GIT_AUTHOR_DATE}" git commit -m "Add my-old-file."

— Martin Burnicki martin.burnicki@burnicki.net 2020-03-18