persistent-https: add go.mod to fix compile

From: Dominyk Tiller <[email protected]>

GOPATH-based builds and non module-aware builds are being deprecated by golang upstream, which currently causes this to fail. This adds a barebones mod file to fix the build.

The persistent-https code hasn't been touched for a long time but I assume this is preferable to simply removing it from the codebase.

Before this change:

```
case $(go version) in \
	"go version go"1.[0-5].*) EQ=" " ;; *) EQ="=" ;; esac && \
	go build -o git-remote-persistent-https \
		-ldflags "-X main._BUILD_EMBED_LABEL${EQ}"
go: cannot find main module, but found .git/config in ../git
	to create a module there, run:
	cd ../.. && go mod init
make: *** [git-remote-persistent-https] Error 1
```

Quoted 10 lines · Dominyk Tiller via GitGitGadget

From: Dominyk Tiller <[email protected]>

GOPATH-based builds and non module-aware builds are being deprecated by golang upstream, which currently causes this to fail. This adds a barebones mod file to fix the build.

The persistent-https code hasn't been touched for a long time but I assume this is preferable to simply removing it from the codebase.

Before this change:

Quoted 10 lines

```
case $(go version) in \
	"go version go"1.[0-5].*) EQ=" " ;; *) EQ="=" ;; esac && \
	go build -o git-remote-persistent-https \
		-ldflags "-X main._BUILD_EMBED_LABEL${EQ}"
go: cannot find main module, but found .git/config in ../git
	to create a module there, run:
	cd ../.. && go mod init
make: *** [git-remote-persistent-https] Error 1
```

With which version of go? Any recent version would fail the same way, or only 1.16 and later?

contrib/persistent-https/go.mod line 3

Quoted 11 lines

Ref: https://blog.golang.org/go116-module-changes.

contrib/persistent-https/go.mod new file +3 -0

new file mode 100644
index 000000000000..6028b1fe5e62
@@ -0,0 +1,3 @@
+module github.com/git/git/contrib/persistent-https
+
+go 1.16

Can I ask what is affected by this 1.16 version number? Do the users have to use 1.16 and nothing older or newer?

As a non Go user, I am trying to see if this change is "make it work for all users of reasonably new versions of Go" (if that is the case, what is the "reasonably new") or "make it work for those with 1.16, and everybody else should either install 1.16 or figure out their own solutions".

Thanks.

Junio C Hamano wrote on 30/03/2021 20:09:

Quoted 22 lines

Quoted 10 lines · Dominyk Tiller via GitGitGadget

From: Dominyk Tiller <[email protected]>

GOPATH-based builds and non module-aware builds are being deprecated by golang upstream, which currently causes this to fail. This adds a barebones mod file to fix the build.

The persistent-https code hasn't been touched for a long time but I assume this is preferable to simply removing it from the codebase.

Before this change:

Quoted 10 lines

```
case $(go version) in \
	"go version go"1.[0-5].*) EQ=" " ;; *) EQ="=" ;; esac && \
	go build -o git-remote-persistent-https \
		-ldflags "-X main._BUILD_EMBED_LABEL${EQ}"
go: cannot find main module, but found .git/config in ../git
	to create a module there, run:
	cd ../.. && go mod init
make: *** [git-remote-persistent-https] Error 1
```

Quoted 2 lines

With which version of go? Any recent version would fail the same way, or only 1.16 and later?

The link I referenced in the notes explains a little more in depth, but there's an environment variable you can use with 1.16 to temporarily mitigate the failure, i.e. export GO111MODULE=off, but regardless of the presence of that the lack of module-awareness will become a hard failure in Go 1.17. The lack of module awareness is only a failure on Go 1.16 and later. Module support was added in basic form as far back as Go 1.11, released late 2018.

Quoted 14 lines

contrib/persistent-https/go.mod line 3

Quoted 11 lines

Ref: https://blog.golang.org/go116-module-changes.

contrib/persistent-https/go.mod new file +3 -0

new file mode 100644
index 000000000000..6028b1fe5e62
@@ -0,0 +1,3 @@
+module github.com/git/git/contrib/persistent-https
+
+go 1.16

Can I ask what is affected by this 1.16 version number? Do the users have to use 1.16 and nothing older or newer?

Quoted 7 lines

As a non Go user, I am trying to see if this change is "make it work for all users of reasonably new versions of Go" (if that is the case, what is the "reasonably new") or "make it work for those with 1.16, and everybody else should either install 1.16 or figure out their own solutions".

Thanks.

This is more thoroughly detailed here:
https://golang.org/ref/mod#go-mod-file-go, but essentially the version number was/is intended to be the minimum Go version the module is designed to work with. We could set it lower to play it safe if the Git project wishes, but to date there have been no backwards incompatibilities with the module system and the way we're using the module system is so basic I don't see any way we'd trigger the version-based behaviours detailed in the link above. For what it's worth testing locally against 1.15 it builds without issue, despite being a lower version number than specified in the string.

In any case, explaining these things in this response is good, but eventually we need to make sure that the readers of the resulting commit would not have to ask the same question, without having to refer to external documentation.

Quoted 4 lines · Junio C Hamano

In any case, explaining these things in this response is good, but eventually we need to make sure that the readers of the resulting commit would not have to ask the same question, without having to refer to external documentation.

It might also be worthwhile -- for the non-Go readers -- for the commit message to mention that this addition of a go.mod file does not hinder those stuck with old pre-module versions of Go (it doesn't help them either, but that's less significant), thus this change does not require them to update to a modern version of Go (i.e. we're not raising the minimum required version).