scripts: add "west gtags" command

This is an extension for indexing the source code in the workspace
with GNU Global. See the command line help for more information about
Global.

Signed-off-by: Martí Bolívar <marti.bolivar@oss.qualcomm.com>

scripts/west-commands.yml

@@ -94,3 +94,8 @@ west-commands:
       - name: patch
         class: Patch
         help: manage patches for Zephyr modules
+  - file: scripts/west_commands/gtags.py
+    commands:
+      - name: gtags
+        class: Gtags
+        help: create a GNU global tags file for the current workspace

scripts/west_commands/gtags.py

@@ -0,0 +1,98 @@
+# Copyright (c) 2025 Qualcomm Innovation Center, Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+"""gtags.py
+
+A west extension for creating tags files (GTAGS) for GNU Global.
+For more information on Global, see: https://www.gnu.org/software/global
+"""
+
+import argparse
+import os.path
+import subprocess
+import tempfile
+
+from west.commands import WestCommand
+
+
+class Gtags(WestCommand):
+    def __init__(self):
+        super().__init__(
+            "gtags",
+            "create a GNU Global tags file for the current workspace",
+            """\
+Indexes source code files in the west workspace using GNU Global's
+"gtags" tool. For more information on Global and gtags, see:
+
+    https://www.gnu.org/software/global/
+
+The index can be useful to find definitions of functions, etc.,
+especially across repository boundaries. One example is
+finding the definition of a vendor HAL function that is
+provided by a Zephyr module for the HAL.
+
+By default, this west command only indexes files that are
+tracked by git projects defined in the west. Inactive west
+projects are ignored by default. For more information on
+projects etc., see the west documentation.""",
+        )
+
+    def do_add_parser(self, parser_adder):
+        parser = parser_adder.add_parser(
+            self.name,
+            help=self.help,
+            description=self.description,
+            formatter_class=argparse.RawDescriptionHelpFormatter,
+        )
+
+        parser.add_argument(
+            "projects",
+            nargs="*",
+            metavar="PROJECT",
+            help="""Name of west project to index, or
+            its path. May be given more than once. Use
+            "manifest" to refer to the manifest
+            repository""",
+        )
+
+        return parser
+
+    def do_run(self, args, unknown_args):
+        all_files = []
+        for project in self.manifest.get_projects(args.projects):
+            all_files.extend(self.files_in_project(project))
+
+        with tempfile.TemporaryDirectory(suffix="gtags") as d:
+            gtags_files = os.path.join(d, "gtags.files")
+            with open(gtags_files, "w") as f:
+                # Due to what looks like a limitation in GNU Global,
+                # this won't work if there are newlines in file names.
+                # Unlike xargs and other commands, though, gtags
+                # doesn't seem to have a way to accept a NUL-delimited
+                # list of input file; its manpage says file names must
+                # be delimited by newlines.
+                f.write("\n".join(all_files))
+            subprocess.run(
+                # Note that "gtags -f -" and passing files via stdin
+                # could run into issues on windows, and there seem to
+                # be win32 builds of global out there
+                ["gtags", "-f", gtags_files],
+                cwd=self.manifest.topdir,
+                check=True,
+            )
+
+    def files_in_project(self, project):
+        if not project.is_cloned() or not self.manifest.is_active(project):
+            return []
+        ls_files = (
+            project.git(["ls-files", "**"], capture_stdout=True).stdout.decode("utf-8").splitlines()
+        )
+        ret = []
+        for filename in ls_files:
+            absolute = os.path.join(project.abspath, filename)
+            # Filter out directories from the git ls-files output.
+            # There didn't seem to be a way to tell it to do that by
+            # itself.
+            if os.path.isfile(absolute):
+                ret.append(absolute)
+        return ret