Add Versioning support

1 files changed, 37 insertions, 0 deletions

diff --git a/BUILD.md b/BUILD.md
index bbd058fd..fa727f1b 100644
--- a/BUILD.md
+++ b/BUILD.md
@@ -15,6 +15,43 @@ Now ready to modify the code and build two binaries, `cmd/gobgp` and `cmd/gobgpd
 
 GoBGP releases are time-based. Minor releases will occur every month ([Semantic Versioning](https://semver.org/)). Major releases occur only when absolutely necessary.
 
+## Versioning
+
+GoBGP has a internal module for version information.
+```internal/pkg/version/version.go``` defines the following variables
+
+```MAJOR``` ```MINOR``` ```PATCH``` these constants are for the Semantic Versioning scheme.
+These will be updated upon release by maintainer.
+
+There is also two more variables that are ment to be changed by ldflags;
+
+```TAG``` is supposed to be used to denote which branch the build is based upon.
+```SHA``` is supposed to be used to inform about which git sha sum the build is based on.
+
+### Examples
+
+A normal release version of GoBGP Version 2.5.0 should should have;
+
+```golang
+const MAJOR uint = 2
+const MINOR uint = 5
+const PATCH uint = 0
+```
+
+If you have a non-standard release and want to have more build information there is some flags to be used.
+`COMMIT`, `IDENTIFIER` and `METADATA`.
+
+```bash
+go build -ldflags \
+	"-X github.com/osrg/gobgp/internal/pkg/version.COMMIT=`git rev-parse --short HEAD` \
+	 -X github.com/osrg/gobgp/internal/pkg/version.METADATA="date.`date "+%Y%m%d"`" \
+	 -X github.com/osrg/gobgp/internal/pkg/version.IDENTIFIER=alpha"
+```
+
+This will produce a version number of
+
+```2.5.0-alpaha+commit.XXXYYYZZ.date.20190526```
+
 ## Layout
 
 The GoBGP project adopts [Standard Go Project Layout](https://github.com/golang-standards/project-layout).