Integrate sparse checkout support and bump minimum Python version to 3.7

README.md

@@ -92,7 +92,7 @@ configured branch, use `./git-external clone`.
                 url = "${ibrvsscloud}/foo"	
                 path = "foo"
                 vcs = none
-- `script = none`: Execute a script after cloning the external
+- `script = none`: Execute a script located at repository root after cloning the external.  Note: not supported on Windows (including git-bash).
 
         [external "foo"]
                 script = run.sh
@@ -109,6 +109,13 @@ configured branch, use `./git-external clone`.
                ...
                updateArgs = --sparse
 
+- `sparseCheckout`: Enable and configure sparse checkout.  If this option is not present or is empty, sparse checkout is disabled.  Note, `--sparse` option to `cloneArgs` or `updateArgs` is not required for this to work.
+
+        [external "foo"]
+               ...
+               sparseCheckout = "bar baz"
+
+
 ## Overrides
 
 You can overide the settings for externals by putting an external

bin/git-external

@@ -304,6 +304,20 @@ class GitExternal:
         ret = cur_branch.stdout.decode().strip()
         return ret or None
 
+    def update_sparse_checkout(self, repo, path, config):
+        """Updates the current set of sparse checkouts"""
+        sparse_checkout = get_args(config, "sparseCheckout")
+        cur_dir = os.curdir
+        os.chdir(path)
+        if sparse_checkout:
+            log.info(f"[{repo}] Setting sparse-checkout to {sparse_checkout}")
+            cmd = ["git", "sparse-checkout", "set"] + sparse_checkout     
+        else:
+            log.info(f"[{repo}] Sparse checkout not in use, disabled")        
+            cmd = ["git", "sparse-checkout", "disable"]
+        check_call(cmd)
+        os.chdir(cur_dir)
+
     def init_or_update(self, recursive=True, only=None, external=None):
         """Init or update all repositories in self.configurations.
 
@@ -355,6 +369,7 @@ class GitExternal:
                         opts = get_args(config, "updateArgs")
                         log.info(f"[{repo}] Updating Git external, {opts}")
                         check_call(["git", "pull", "--ff-only"] + opts, cwd=path)
+                        self.update_sparse_checkout(repo, path, config)
                     elif cur_branch is None:
                         log.warning(f"[{repo}] Skipping update, detached HEAD")
                     else:
@@ -407,7 +422,7 @@ class GitExternal:
                     cmd = ["git", "clone"] + opts + [config["url"], path]
                     print(" ".join(cmd))
                     check_call(cmd)
-
+                    self.update_sparse_checkout(repo, path, config)
                     cur_branch = self.get_branch_name(path)
                     branch = config.get('branch') or "master"
                     if cur_branch != branch:

setup.py

@@ -18,6 +18,6 @@
       ],
       zip_safe=False,
       scripts=['bin/git-external'],
-      python_requires='>=3.6'
+      python_requires='>=3.7'
 )