HEAD independent version script

README.md

@@ -180,13 +180,13 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 ## Developer tips
 
-If you're adding additional compatibility code to this package, the [`bin/version.sh` script is useful for extracting the version number from a git commit SHA. For example, from the git repository of `julia`, run something like this:
+If you're adding additional compatibility code to this package, the [`bin/version.sh`](https://github.com/JuliaLang/Compat.jl/blob/master/bin/version.sh) script is useful for extracting the version number from a git commit SHA. For example, from the git repository of `julia`, run something like this:
 
 ```sh
 bash $ /path/to/Compat/bin/version.sh a378b60fe483130d0d30206deb8ba662e93944da
 0.5.0-dev+2023
 ```
 
-This prints a number `XXXX`, and you can then test whether Julia
-is at least this version by `VERSION >= v"0.Y.0-dev+XXXX"` (assuming
-it is a commit from the 0.Y development cycle).
+This prints a version number corresponding to the specified commit of the form
+`X.Y.Z-aaa+NNNN`, and you can then test whether Julia
+is at least this version by `VERSION >= v"X.Y.Z-aaa+NNNN"`.

bin/version.sh

@@ -1,5 +1,11 @@
 #!/bin/bash
-last_tag=$(git describe --tags --abbrev=0)
-ver=$(cat VERSION)
-nb=$(git rev-list $1 ^$last_tag | wc -l | sed -e 's/[^[:digit:]]//g')
+
+# Need to be run from a julia repo clone
+# First argument (Optional) is a ref to the commit
+
+gitref=${1:-HEAD}
+
+last_tag=$(git describe --tags --abbrev=0 "$gitref")
+ver=$(git show "$gitref:VERSION")
+nb=$(git rev-list --count "$gitref" "^$last_tag")
 echo "$ver+$nb"