Automatically publish builds from Travis (#92)

.travis.yml

@@ -9,8 +9,19 @@ install:
   - docker-compose build
   - docker-compose up -d
 script:
+  - docker-compose run --rm --volume "$PWD/dist:/src/dist" dbmate make build
   - docker-compose run --rm dbmate make wait
   - docker-compose run --rm dbmate make test
   - docker-compose run --rm dbmate make lint
   - docker build -t dbmate .
   - docker run --rm dbmate --help
+deploy:
+  provider: releases
+  api_key:
+    secure: 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
+  file_glob: true
+  file: dist/*
+  skip_cleanup: true
+  on:
+    tags: true
+    repo: amacneil/dbmate

Makefile

@@ -18,7 +18,7 @@ wait:
 
 .PHONY: clean
 clean:
-	rm -rf dist
+	rm -rf dist/*
 
 .PHONY: build
 build: clean build-linux build-macos build-windows

RELEASING.md

@@ -4,7 +4,7 @@ The following steps should be followed to publish a new version of dbmate (requi
 
 1. Update [version.go](/pkg/dbmate/version.go) and [README.md](/README.md) with new version number ([example PR](https://github.com/amacneil/dbmate/pull/79/files))
 2. Create new release on GitHub project [releases page](https://github.com/amacneil/dbmate/releases)
-3. Build using `make docker` and upload contents of `dist/` directory as assets attached to the GitHub release
+3. Travis CI will automatically publish release binaries to GitHub
 4. Create PR to update Homebrew package by running the following command:
 
 ```