Find external package for git-lfs. (#18107)

var/spack/repos/builtin/packages/git-lfs/package.py

@@ -3,6 +3,7 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+import re
 from spack import *
 
 
@@ -16,6 +17,8 @@ class GitLfs(MakefilePackage):
     homepage = "https://git-lfs.github.com"
     url      = "https://github.com/git-lfs/git-lfs/archive/v2.6.1.tar.gz"
 
+    executables = ['^git-lfs$']
+
     version('2.11.0', sha256='8183c4cbef8cf9c2e86b0c0a9822451e2df272f89ceb357c498bfdf0ff1b36c7')
     version('2.10.0', sha256='07fd5c57a1039d5717dc192affbe3268ec2fd03accdca462cb504c0b4194cd23')
     version('2.9.0', sha256='f1963ad88747577ffeeb854649aeacaa741c59be74683da4d46b129a72d111b7')
@@ -32,6 +35,12 @@ class GitLfs(MakefilePackage):
 
     parallel = False
 
+    @classmethod
+    def determine_version(cls, exe):
+        output = Executable(exe)('--version', output=str, error=str)
+        match = re.search(r'git-lfs/(\S+)', output)
+        return match.group(1) if match else None
+
     # Git-lfs does not provide an 'install' target in the Makefile
     def install(self, spec, prefix):
         mkdirp(prefix.bin)