Re: [PATCH 0/5] Introduce configs for default repo format

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Aug 15, 2024, 21:16 UTC
Message-ID: <Zr5wODo8tgGtPEIM@tapette.crustytoothpaste.net>
In-Reply-To: <Zr4dvybR6j6Ifyya@ArchLinux>

On 2024-08-15 at 15:24:47, shejialuo wrote:

Show 15 quoted lines

> If the user uses the following command:
> 
>   $ export GIT_DEFAULT_HASH_ENVIRONMENT=sha1
>   $ git -c init.defaultObjectFormat=sha256 repo
> 
> The repo would be initialized with the sha1 algorithm. I think we should
> think carefully which precedence should be higher. I cannot give an
> answer here. I am not familiar with the whole database and do not the
> concern. But from my own perspective, I think the precedence of the
> config should be higher than the environment variable. This is a new
> feature, the people who would like to use it, they will never use
> environment variable and we should ignore the functionality of the
> environment variable. But for people who do not know this feature, they
> will continue to use the environment variable and they will never be
> influenced by the configs.

The standard behaviour we have with other environment variables is that they override the config, such as with `GIT_SSH_COMMAND` and `GIT_SSH_VARIANT`. The reason is that the config in this case is usually per-user or per-system, but it's very common to override settings on an ephemeral basis with the environment.

Think of the case where you have a language package manager that's creating a repository or fetching from one. You can override on the command line with `GIT_DEFAULT_HASH` or `GIT_SSH_VARIANT`, but you can't control the actual `git` invocation, since it's baked into the package manager. Or if you're writing a test and need all of the Git commands to use a particular setting, then it's easy to simply set the environment once and forget about it. (This is what we do at $DAYJOB to implement SHA-256 test modes for our repos: the test script sets `GIT_DEFAULT_HASH` and all of our test repos magically use the right setting.)

-- 
brian m. carlson (they/them or he/him)
Toronto, Ontario, CA