Document and test empty Git versions

If libnitrokey has not been built from a clone of the Git repository,
the Git version string may be empty.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/lib.rs b/src/lib.rs
index c4e55b1..02a622b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -111,12 +111,13 @@ pub use crate::util::{CommandError, LogLevel};
 /// version.
 #[derive(Clone, Debug, PartialEq)]
 pub struct Version {
-    /// The library version as a string.
+    /// The Git library version as a string.
     ///
     /// The library version is the output of `git describe --always` at compile time, for example
     /// `v3.3` or `v3.4.1`.  If the library has not been built from a release, the version string
     /// contains the number of commits since the last release and the hash of the current commit, for
-    /// example `v3.3-19-gaee920b`.
+    /// example `v3.3-19-gaee920b`.  If the library has not been built from a Git checkout, this
+    /// string may be empty.
     pub git: String,
     /// The major library version.
     pub major: u32,