build: Add git ref to the binary

In order to be able to figure out which binary is in use (for example
in debugging situation) it's really helpful to have the 'git describe'
ref added to the binary.

The simplest way to expose the it via good old Source Code Control
System string id. No need to come up with something complicated else
as there is no agreement on how to do this. So let's add this simple
magic string to library.

You can either query with 'what' or just

  $strings .build/src/libnvme.so | grep '@(#)'
  @(#)libnvme 1.0-1-g5ff5d22+

The idea how to extract the version string is shamelessly copied from
the systemd project.

Signed-off-by: Daniel Wagner <[email protected]>

Author: dwsuse

meson-vcs-tag.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+set -eu
+set -o pipefail
+
+dir="${1:?}"
+fallback="${2:?}"
+
+# Apparently git describe has a bug where it always considers the work-tree
+# dirty when invoked with --git-dir (even though 'git status' is happy). Work
+# around this issue by cd-ing to the source directory.
+cd "$dir"
+# Check that we have either .git/ (a normal clone) or a .git file (a work-tree)
+# and that we don't get confused if a tarball is extracted in a higher-level
+# git repository.
+[ -e .git ] && git describe --abbrev=7 --dirty=+ 2>/dev/null | sed 's/^v//' || echo "$fallback"

meson.build

@@ -36,6 +36,17 @@ pkgconfiglibdir = get_option('pkgconfiglibdir') == '' ? join_paths(libdir, 'pkgc
 ################################################################################
 conf = configuration_data()
 
+version_tag = get_option('version-tag')
+if version_tag != ''
+        conf.set('GIT_VERSION', '"@0@"'.format(version_tag))
+else
+    r = run_command('meson-vcs-tag.sh',
+                    meson.current_source_dir(),
+                    meson.project_version(),
+                    check: true)
+    conf.set('GIT_VERSION', '"@0@"'.format(r.stdout().strip()))
+endif
+
 conf.set('SYSCONFDIR', '"@0@"'.format(sysconfdir))
 
 # Check for libuuid availability

meson_options.txt

@@ -1,4 +1,5 @@
 # -*- mode: meson -*-
+option('version-tag', type : 'string', description : 'override the git version string')
 option('pkgconfiglibdir', type : 'string', value : '', description : 'directory for standard pkg-config files')
 option('htmldir', type : 'string', value : '', description : 'directory for HTML documentation')
 

src/nvme/util.c

@@ -23,6 +23,9 @@
 #include "util.h"
 #include "log.h"
 
+/* Source Code Control System, query version of binary with 'what' */
+const char sccsid[] = "@(#)libnvme " GIT_VERSION;
+
 static inline __u8 nvme_generic_status_to_errno(__u16 status)
 {
 	switch (status) {