version: Use linker flag

Embedding the version file is slightly annoying for packaging, because
the release tarball is not a git repository and so "go generate" would
fail. Instead a packager would have to manually create the version.txt
file.
With using a linker flag, the version string has a graceful fallback.

.build.yml

@@ -11,7 +11,6 @@ sources:
 tasks:
     - test: |
           cd ntfy-alertmanager
-          go generate ./...
           go test -v ./...
     - lint: |
           cd ntfy-alertmanager

.gitignore

@@ -1,2 +1 @@
 /ntfy-alertmanager
-version.txt

docker/Dockerfile-dev

@@ -3,7 +3,7 @@ WORKDIR /app
 
 COPY . .
 RUN apk add --no-cache git
-RUN go generate ./... && go build -o /app/ntfy-alertmanager
+RUN go build -ldflags="-X main.version=$(git describe --long)" -o /app/ntfy-alertmanager
 
 
 FROM alpine:latest

main.go

@@ -19,9 +19,7 @@ import (
 	"golang.org/x/text/language"
 )
 
-//go:generate sh -c "git describe --long > version.txt"
+var version = "dev"
-//go:embed version.txt
-var version string
 
 type receiver struct {
 	cfg    *config