chore(ci): fix default branch in Dockerfiles (#875)

build.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
 
-VERSION=$(git describe)
+VERSION=$(git describe --tags)
 echo "Building $VERSION..."
-go build -o watchtower -ldflags "-X github.com/containrrr/watchtower/cmd.version=$VERSION"
+go build -o watchtower -ldflags "-X github.com/containrrr/watchtower/cmd.version=$VERSION"

dockerfiles/Dockerfile.dev-self-contained

@@ -4,8 +4,8 @@
 
 FROM golang:alpine as builder
 
-# use version (for example "v0.3.3") or "master"
-ARG WATCHTOWER_VERSION=master
+# use version (for example "v0.3.3") or "main"
+ARG WATCHTOWER_VERSION=main
 
 RUN apk add --no-cache \
     alpine-sdk \
@@ -18,7 +18,7 @@ COPY . /watchtower
 RUN \
   cd /watchtower && \
   \
-  GO111MODULE=on CGO_ENABLED=0 GOOS=linux go build -a -ldflags '-extldflags "-static"' . && \
+  GO111MODULE=on CGO_ENABLED=0 GOOS=linux go build -a -ldflags "-extldflags '-static' -X github.com/containrrr/watchtower/cmd.version=$(git describe --tags)" . && \
   GO111MODULE=on go test ./... -v
 
 

dockerfiles/Dockerfile.self-contained

@@ -4,8 +4,8 @@
 
 FROM golang:alpine as builder
 
-# use version (for example "v0.3.3") or "master"
-ARG WATCHTOWER_VERSION=master
+# use version (for example "v0.3.3") or "main"
+ARG WATCHTOWER_VERSION=main
 
 RUN apk add --no-cache \
     alpine-sdk \
@@ -18,7 +18,7 @@ RUN git clone --branch "${WATCHTOWER_VERSION}" https://github.com/containrrr/wat
 RUN \
   cd watchtower && \
   \
-  GO111MODULE=on CGO_ENABLED=0 GOOS=linux go build -a -ldflags '-extldflags "-static"' . && \
+  GO111MODULE=on CGO_ENABLED=0 GOOS=linux go build -a -ldflags "-extldflags '-static' -X github.com/containrrr/watchtower/cmd.version=$(git describe --tags)" . && \
   GO111MODULE=on go test ./... -v