Include GIT SHA in the binary builds

[rshriram]

Sometimes, its hard to identify if Bazel built the binary or not.. It would be nice to include all the git commit versions into the binary so that we can be sure that it is using the current version.

For example, in amalgam8 we use something like this:

BUILD_SYM	:= github.com/amalgam8/amalgam8/pkg/version
LDFLAGS		+= -X $(BUILD_SYM).version=$(APP_VER)
LDFLAGS		+= -X $(BUILD_SYM).gitRevision=$(shell git rev-parse --short HEAD 2> /dev/null  || echo unknown)
LDFLAGS		+= -X $(BUILD_SYM).branch=$(shell git rev-parse --abbrev-ref HEAD 2> /dev/null  || echo unknown)
LDFLAGS		+= -X $(BUILD_SYM).buildUser=$(shell whoami || echo nobody)@$(shell hostname -f || echo builder)
LDFLAGS		+= -X $(BUILD_SYM).buildDate=$(shell date +%Y-%m-%dT%H:%M:%S%:z)
LDFLAGS		+= -X $(BUILD_SYM).goVersion=$(word 3,$(shell go version))

We need an equivalent in bazel. Could someone help with this please?

[kyessenov]

Do you use go codegen or a bash script for this?

[rshriram]

It's in our makefile. We use the ldflags during go build. No scripts or code gen needed.

[kyessenov]

I see. I can write a bazel script to fill up a go source file. go tool would use the default values then.

[rshriram]

Well we need to have a go file like the one mentioned above https://github.com/amalgam8/amalgam8/blob/master/pkg/version/version.go

[rshriram]

Do we need to write a Go file ? Cant we make bazel include ldflags ?

go build $(BUILDFLAGS) -ldflags '$(LDFLAGS)' ...

[rshriram]

basically we just include the same version file in our code. Populate the vars at compile time (as shown above), stick them into ldflags and compile.

[ayj]

go_binary's linkstamp attribute may be of some use here.

linkstamp String; optional; default is ""

The name of a package containing global variables set by the linker as part of a link stamp. This may be used to embed version information in the generated binary. The -X flags will be of the form -X linkstamp.KEY=VALUE. The keys and values are read from bazel-bin/volatile-status.txt and bazel-bin/stable-status.txt. If you build with --workspace_status_command=./status.sh, the output of status.sh will be written to these files. Bazel tools/buildstamp/get_workspace_status is a good template which prints Git workspace status.

[ayj]

Implemented in #265