Pkg.jl: Use @ to specify branches + commits in REPL?

[KristofferC]

Gets rid of the # and @ distinction. Priority is given to versions.

See https://discourse.julialang.org/t/pkg-add-at-or-trackto-or/12270.

[StefanKarpinski]

It seems like—in classic git-CLI-"spectacle of inconsistency" fashion—when there's a tag and a branch with the same name some git commands prefer the tag while others prefer the branch:

https://softwareengineering.stackexchange.com/questions/230438/in-git-is-it-a-bad-idea-to-create-a-tag-with-the-same-name-as-a-deleted-branch
https://groups.google.com/forum/#!topic/git-users/FfzGmqj6sNQ

So we're free to pick whatever behavior we think is sane here.

[KristofferC]

It seems kinda annoying to do pkg> add [email protected], there only exists a Foo version 0.6.2 and then get an error message about that the branch 0.6.3 doesn't exist.

[fredrikekre]

FWIW it does not bother me that we have both # and @, you learn it once and then you know what to use.

[StefanKarpinski]

ASCII syntax is precious though and we may want to hold it in reserve for other future meanings.

[GunnarFarneback]

One advantage of keeping # rather than @ is that git@gitlab... and similar URLs need less explanation that @ means something else in that context.

[i-apellaniz]

Indeed I also prefer the # syntax. For the error message when 0.6.3 tag doesn't exist but 0.6.2 does, the Pkg has to try to search among the branches. Hence, the error could look like: Pkg cannot find any version or branch for Foo with the name 0.6.3. This way the user is aware that Pkg looks for both tags and branches.

I also created a branch using the SHA hash of a commit. It seems that git prefers to switch between branches and not to go to the commit.

IMHO, Pkg should use only a single character, say #, and then look first for TAGs, then for BRANCHes (print a proper error if it does not succeed), and finally for COMMITS (if it is a valid SHA key). Here is a sketch of what can be done. It's only an ides and, for sure that I miss something or I make some mistake :)

(pkg) pkg> add Foo#__key__

|__key__ | empty | is TAG? | is BRANCH? | is COMMIT? |
|---:|---:|---:|---:|---:|
Action | Download released, check for updates as add Foo does. OR print an error saying that key cannot be empty | Download __key__ among releases or TAGs and "pin" it | Clone it, and track for updates nightly. Print Installed and tracking for nightly or something like that | Only if valid SHA Download snapshot and "pin" it |

If It does not succeed tell the user if Pkg has looked at TAGs and BRANCHes, or if it has looked at all possibilities, TAGs, BRANCHes and COMMITs

ERROR: Pkg cannot find any version or branch __key__ for Foo
ERROR: Pkg cannot find any version, branch or commit __key__ for Foo

[KristofferC]

Let's just keep it the way it is.