49: Use a Personal Access Token to access private modules. (#4)

I left it unchanged in the PR, but I would recommend a variable name other than `GITEA_TOKEN`, as I suspect that will be used by Gitea at some future date--like Github use `GITHUB_TOKEN`--and cause confusion since this is not the same token.

Something like `GIT_VDB_TO_TOKEN` might do, since we could follow the `HOST_NAME_TOKEN` pattern for other repos if needed.

Co-authored-by: Thomas E Lackey <telackey@bozemanpass.com>
Reviewed-on: #4
Co-authored-by: Thomas E Lackey <telackey@noreply.git.vdb.to>
Co-committed-by: Thomas E Lackey <telackey@noreply.git.vdb.to>

Dockerfile

@@ -5,21 +5,18 @@ RUN apk add --no-cache gcc musl-dev binutils-gold linux-headers git
 
 # Configure creds for gitea
 ARG GITEA_TOKEN
-RUN echo $GITEA_TOKEN > ~/.token
-RUN git config --global credential.username _ # ignored, but prevents prompt
-RUN git config --global credential.helper \
-    '!f() { test "$1" = get && echo "password=$(cat $HOME/.token)"; }; f'
-
-WORKDIR /plugeth-statediff/
 
 # Get and cache deps
+WORKDIR /plugeth-statediff/
 COPY go.mod .
 COPY go.sum .
-RUN go mod download
+RUN if [ -n "$GITEA_TOKEN" ]; then git config --global url."https://$GITEA_TOKEN:@git.vdb.to/".insteadOf "https://git.vdb.to/"; fi && \
+    go mod download && \
+    rm -f ~/.gitconfig
 
 ADD . .
 RUN go build --tags linkgeth --buildmode=plugin --trimpath -o statediff.so ./main
 
-FROM alpine:latest
+FROM alpine:3.18
 
 COPY --from=builder /plugeth-statediff/statediff.so /usr/local/lib/