Merge ~cjwatson/turnip/+git/turnipcake:publish-swift-build-label into ~canonical-launchpad-branches/turnip/+git/turnipcake:master

[Colin Watson]

Publish last-successful-build-label.txt to Swift

This makes it easier for the Mojo spec to find the most recently-built revision, since it can't necessarily enumerate files in the Swift container.

Same as https://code.launchpad.net/~cjwatson/turnip/+git/turnip/+merge/387744, but for turnipcake.

[Thiago F. Pappacena (pappacena)]

LGTM

review: Approve

diff --git a/Makefile b/Makefile
index ce0d72f..6c87e2a 100644
--- a/Makefile
+++ b/Makefile
@@ -114,6 +114,6 @@ publish-tarball: build-tarball
 	[ ! -e ~/.config/swift/turnip ] || . ~/.config/swift/turnip; \
 	./publish-to-swift --debug \
 		$(SWIFT_CONTAINER_NAME) $(SWIFT_OBJECT_PATH) \
-		$(TARBALL_BUILD_PATH)
+		$(TARBALL_BUILD_PATH) turnipcake=$(TARBALL_BUILD_LABEL)
 
 .PHONY: build check clean dist lint run migrate build-tarball publish-tarball
diff --git a/publish-to-swift b/publish-to-swift
index e5cfd59..5a86fe7 100755
--- a/publish-to-swift
+++ b/publish-to-swift
@@ -7,6 +7,7 @@ import os
 import re
 import subprocess
 import sys
+import tempfile
 
 
 def ensure_container_privs(container_name):
@@ -75,6 +76,7 @@ def main():
     parser.add_argument("container_name")
     parser.add_argument("swift_object_path")
     parser.add_argument("local_path")
+    parser.add_argument("build_label")
     args = parser.parse_args()
 
     if args.debug:
@@ -118,6 +120,14 @@ def main():
         args.container_name, args.swift_object_path, args.local_path,
         overwrite=overwrite)
 
+    with tempfile.TemporaryDirectory() as tmpdir:
+        filename = "last-successful-build-label.txt"
+        with open(os.path.join(tmpdir, filename), "w") as f:
+            f.write(args.build_label)
+        publish_file_to_swift(
+            args.container_name, filename, os.path.join(tmpdir, filename),
+            overwrite=True)
+
 
 if __name__ == "__main__":
     main()