On Thu, Apr 08 2021, Junio C Hamano wrote: > Patrick Steinhardt <ps@xxxxxx> writes: > [...] >> Introduce a new GIT_CONFIG_NOGLOBAL envvar, which is the simple >> equivalent to GIT_CONFIG_NOSYSTEM. If set to true, git will skip reading >> both `~/.gitconfig` and `$XDG_CONFIG_HOME/git/config`. > > I do not think we'd add an unbounded number of new configuration > sources to the existing three-level hierarchy of system-wide > (/etc/gitconfig), per-user ($HOME/.gitconfig), and local > (.git/config), so it is not too bad, from scalability point of view, > to keep adding new GIT_CONFIG_NO$FROTZ variables. > > Let me go in a couple of different tangents a bit, thinking aloud. > > Tangent One. I wonder if the presense of includeIf.<cond>.path > changes the "we won't have unbounded, so adding another here is OK" > reasoning. If somebody wanted to say "Do not use the paths that > match this and that pattern", it is likely that we'd end up having > to support a single variable that allows more than one "value". In > a straw-man syntax "GIT_CONFIG_EXCLUDE='/home/gitster/* > /home/peff/*'" might be a way to say "do not use files that are > under these two directories. > > And when that happens, we'd probably notice that it is easier for > users to configure, if they can treat 'system' and 'global' as just > another special pattern to place on that list. //system and //global > might be the syntax we'd choose when time comes, i.e. > > GIT_CONFIG_EXCLUDE='//system //global' > > might become a more scalable replacement for > > GIT_CONFIG_NOSYSTEM=yes GIT_CONFIG_NOHOME=yes > > Tangent Two. One thing we never managed to properly test in our > test suite is the unctioning of GIT_CONFIG_NOSYSTEM. As we do not > want to get broken by whatever is in /etc/gitconfig, all our tests > run with the environment variable set. For the same reason, in > order to avoid getting influenced by whatever the tester has in > $HOME/.gitconfig, we export HOME set to the throw-away directory > created during the test and control what is in the config file in > that directory. In hindsight, it might have been a better design to > use GIT_CONFIG_SYSTEM variable that points at a path to be used as a > replacement for /etc/gitconfig when it is set; pointing /dev/null > with the variable would have been the natural way to say "do not use > anything from system configuration". And GIT_CONFIG_GLOBAL can > easily follow the same pattern. > > So, from these two perspective, for the longer term end-user > experience, I am not 100% onboard with GIT_CONFIG_NOGLOBAL. An > alternative that allows us to move away from GIT_CONFIG_NOSYSTEM in > the direction to the tangent #2 would be not to repeat the same > mistake by doing GIT_CONFIG_NOGLOBAL, and instead adding > GIT_CONFIG_GLOBAL, which is > > (1) when not set, it does not do anything, > > (2) when set to "/dev/null" (a literal string; you do not have to > spell it "NUL" when on Windows), it acts just like the case > where your GIT_CONFIG_NOSYSTEM is set, > > (3) when set to any other string, it is taken as a filename that > has the global configuration. Unlike $HOME/.gitconfig or > $XDG_HOME/git/config, it is an error if the named file does not > exist (this is to catch misconfiguration). > > And once this is accepted by users and established as a pattern, we > could migrate GIT_CONFIG_NOSYSTEM to GIT_CONFIG_SYSTEM=/dev/null > > > Having said all that (meaning: I am not 100% onboard with _NOGLOBAL > and think _GLOBAL=/dev/null might be a better design), let's give it > a review under the assumption that _NOGLOBAL is the design we would > want to choose. I think doing this via env vars is inherently nasty, but can't think of a good way to implement it properly without major refactoring. IMO the "properly" would be that we'd just support this sort of thing as first-class config syntax, as I've suggested before e.g. in the repo hooks/config topic. But to do that we couldn't "stream" the config reading as we do now, we'd need to read system/global/local, and when we saw some new meta-syntax apply those ignores to files we already read, and only then start streaming things to config callbacks. See "config.ignore.*" in https://lore.kernel.org/git/87y2ebo16v.fsf@xxxxxxxxxxxxxxxxxxx/
