====== 'git' Environment and Overriding Settings ======

===== Overriding Default Settings =====

==== Environment Variables To Specify Author And Committer ====

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 

<codedoc code>
export GIT_AUTHOR_NAME=~~codedoc:<em>"Martin Burnicki"</em>~~
export GIT_AUTHOR_EMAIL=~~codedoc:<em>"martin.burnicki@burnicki.net"</em>~~
export GIT_COMMITTER_NAME=${GIT_AUTHOR_NAME}
export GIT_COMMITTER_EMAIL=${GIT_AUTHOR_EMAIL}
git commit -m ~~codedoc:<em>"My sudo commit"</em>~~
</codedoc>

or for a single command:

<codedoc code>
GIT_AUTHOR_NAME=~~codedoc:<em>"Martin Burnicki"</em>~~ GIT_AUTHOR_EMAIL=~~codedoc:<em>"martin.burnicki@burnicki.net"</em>~~ GIT_COMMITTER_NAME=${GIT_AUTHOR_NAME} GIT_COMMITTER_EMAIL=${GIT_AUTHOR_EMAIL} git commit -m ~~codedoc:<em>"My sudo commit"</em>~~
</codedoc>


\\
==== Environment Variables To Specify Commit Dates ====

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.


\\
==== Using A Non-Standard Name For The Local '.git' Directory ====

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.:

<codedoc code>
GIT_DIR=~~codedoc:<em>.git-repo-1</em>~~ gitk &
git ~~codedoc:clean:--~~git-dir=~~codedoc:<em>.git-repo-1</em>~~ fetch
</codedoc>


\\
===== Working With 'git' Dates =====

''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:

/* Don't use codedoc here, this would create real email address links */
<code>
commit 7590a8c4a730ec889798497db259e91ef701caec
Author: Martin Burnicki <martin.burnicki@burnicki.net>
Date:   Fri Mar 29 12:44:04 2019 +0100
</code>

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

/* Don't use codedoc here, this would create real email address links */
<code>
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
</code>


\\
==== Overriding 'git' Dates ====

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 ===

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

<codedoc code>
git commit -m ~~codedoc:<em>"My commit message."</em>~~ ~~codedoc:clean:--~~date=~~codedoc:<b>"2023-04-01 13:45"</b>~~
</codedoc>

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


\\
=== Environment variables GIT_AUTHOR_DATE and GIT_COMMITTER_DATE ===

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.

<codedoc code>
GIT_AUTHOR_DATE=~~codedoc:<b>"2023-04-01 13:45"</b>~~ GIT_COMMITTER_DATE=~~codedoc:<b>"2023-04-01 15:45"</b>~~ git commit -m ~~codedoc:<em>"My commit message."</em>~~
</codedoc>

sets the dates to specified but different values, while

<codedoc code>
GIT_AUTHOR_DATE=~~codedoc:<b>"2023-04-01 13:45"</b>~~ GIT_COMMITTER_DATE="${GIT_AUTHOR_DATE}" git commit -m ~~codedoc:<em>"My commit message."</em>~~
</codedoc>

sets them both to the same value.


\\
==== Check In An Existing Old File With Its Original Date ====

When old files from an existing project are to be imported into a newly created 'git' repo,
[[#Environment Variables To Specify Author And Committer|environment variables]]
can be used to set the commit dates to the original file date, and thus maintain
the original file history.

<codedoc code>
git add -f ~~codedoc:<em>my-old-file</em>~~
GIT_AUTHOR_DATE=~~codedoc:<b>"2016-06-11 16:29:04"</b>~~ GIT_COMMITTER_DATE="${GIT_AUTHOR_DATE}" git commit -m ~~codedoc:<em>"Add my-old-file."</em>~~
</codedoc>

----

 --- //Martin Burnicki [[martin.burnicki@burnicki.net]] 2020-03-18//