selfupdate: dont detect FUSE if build is static

Before this patch selfupdate detected ANY build with cmount tag as a build
having libFUSE capabilities. However, only dynamic builds really have it.
The official linux builds are static and have the cmount tag as of the time
of this writing. This results in inability to update official linux binaries.
This patch fixes that. The build can be fixed independently.

cmd/cmount/mount.go

@@ -21,6 +21,7 @@ import (
 	"github.com/rclone/rclone/cmd/mountlib"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/lib/atexit"
+	"github.com/rclone/rclone/lib/buildinfo"
 	"github.com/rclone/rclone/vfs"
 )
 
@@ -35,6 +36,7 @@ func init() {
 		cmd.Aliases = append(cmd.Aliases, "cmount")
 	}
 	mountlib.AddRc("cmount", mount)
+	buildinfo.Tags = append(buildinfo.Tags, "cmount")
 }
 
 // Find the option string in the current options

cmd/selfupdate/help.go

@@ -27,7 +27,7 @@ If the old version contains only dots and digits (for example |v1.54.0|)
 then it's a stable release so you won't need the |--beta| flag. Beta releases
 have an additional information similar to |v1.54.0-beta.5111.06f1c0c61|.
 (if you are a developer and use a locally built rclone, the version number
-will end with |-DEV|, you will have to rebuild it as it obvisously can't
+will end with |-DEV|, you will have to rebuild it as it obviously can't
 be distributed).
 
 If you previously installed rclone via a package manager, the package may

cmd/selfupdate/selfupdate.go

@@ -143,14 +143,9 @@ func InstallUpdate(ctx context.Context, opt *Options) error {
 		return errors.New("--stable and --beta are mutually exclusive")
 	}
 
-	gotCmount := false
-	for _, tag := range buildinfo.Tags {
-		if tag == "cmount" {
-			gotCmount = true
-			break
-		}
-	}
-	if gotCmount && !cmount.ProvidedBy(runtime.GOOS) {
+	// The `cmount` tag is added by cmd/cmount/mount.go only if build is static.
+	_, tags := buildinfo.GetLinkingAndTags()
+	if strings.Contains(" "+tags+" ", " cmount ") && !cmount.ProvidedBy(runtime.GOOS) {
 		return errors.New("updating would discard the mount FUSE capability, aborting")
 	}
 

lib/buildinfo/cmount.go

@@ -1,7 +0,0 @@
-// +build cmount
-
-package buildinfo
-
-func init() {
-	Tags = append(Tags, "cmount")
-}

lib/buildinfo/tags.go

@@ -6,6 +6,8 @@ import (
 )
 
 // Tags contains slice of build tags
+// The `cmount` tag is added by cmd/cmount/mount.go only if build is static.
+// Other tags including `cgo` are detected in this package.
 var Tags []string
 
 // GetLinkingAndTags tells how the rclone executable was linked