use git describe output in long version rather than just rev

Filter for only numeric tags that correspond to main releases rather
than the tags for versions of library crates.

Author: aswild

build.rs

@@ -47,12 +47,14 @@ fn main() {
     // Make the current git hash available to the build.
     if let Some(rev) = git_revision_hash() {
         println!("cargo:rustc-env=RIPGREP_BUILD_GIT_HASH={}", rev);
+        println!("cargo:rerun-if-changed=.git/index");
+        println!("cargo:rerun-if-changed=.git/HEAD");
     }
 }
 
 fn git_revision_hash() -> Option<String> {
     let result = process::Command::new("git")
-        .args(&["rev-parse", "--short=10", "HEAD"])
+        .args(&["describe", "--tags", "--match=[0-9]*", "--dirty=+"])
         .output();
     result.ok().and_then(|output| {
         let v = String::from_utf8_lossy(&output.stdout).trim().to_string();