Raise minimum Go version to 1.9

The golang.org/sys/crypto library uses math/bits, which was only
introduced in Go 1.9.

.travis.yml

@@ -3,10 +3,6 @@ sudo: false
 
 matrix:
   include:
-    - os: linux
-      go: "1.8.x"
-      env: RESTIC_TEST_FUSE=0 RESTIC_TEST_CLOUD_BACKENDS=0
-
     - os: linux
       go: "1.9.x"
       env: RESTIC_TEST_FUSE=0 RESTIC_TEST_CLOUD_BACKENDS=0

build.go

@@ -53,7 +53,7 @@ var config = Config{
 		"github.com/restic/restic/internal/...",
 		"github.com/restic/restic/cmd/...",
 	},
-	MinVersion: GoVersion{Major: 1, Minor: 8, Patch: 0}, // minimum Go version supported
+	MinVersion: GoVersion{Major: 1, Minor: 9, Patch: 0}, // minimum Go version supported
 }
 
 // Config configures the build.

changelog/unreleased/issue-1758

@@ -0,0 +1,8 @@
+Enhancement: Allow saving OneDrive folders in Windows
+
+Restic now contains a bugfix to two libraries, which allows saving OneDrive
+folders in Windows. In order to use the newer versions of the libraries, the
+minimal version required to compile restic is now Go 1.9.
+
+https://github.com/restic/restic/issues/1758
+https://github.com/restic/restic/pull/1765

doc/020_installation.rst

@@ -161,7 +161,7 @@ From Source
 ***********
 
 restic is written in the Go programming language and you need at least
-Go version 1.8. Building restic may also work with older versions of Go,
+Go version 1.9. Building restic may also work with older versions of Go,
 but that's not supported. See the `Getting
 started <https://golang.org/doc/install>`__ guide of the Go project for
 instructions how to install Go.