[PATCH] erofs-utils: generate version number from git commit

[Gao Xiang <xiang@kernel.org>]

In order to make the version string more precise.

Signed-off-by: Gao Xiang <xiang@kernel.org>
---
 configure.ac               |  2 +-
 scripts/get-version-number | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100755 scripts/get-version-number

diff --git a/configure.ac b/configure.ac
index 7217cf531265..38c371c4910f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3,7 +3,7 @@
 
 AC_PREREQ([2.69])
 
-m4_define([erofs_utils_version], m4_esyscmd([sed -n '1p' VERSION | tr -d '\n']))
+m4_define([erofs_utils_version], m4_esyscmd_s([scripts/get-version-number]))
 m4_define([erofs_utils_date], m4_esyscmd([sed -n '2p' VERSION | tr -d '\n']))
 
 AC_INIT([erofs-utils], [erofs_utils_version], [linux-erofs@lists.ozlabs.org])
diff --git a/scripts/get-version-number b/scripts/get-version-number
new file mode 100755
index 000000000000..26f0b5acb753
--- /dev/null
+++ b/scripts/get-version-number
@@ -0,0 +1,33 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+scm_version()
+{
+	# Check for git and a git repo.
+	if test -z "$(git rev-parse --show-cdup 2>/dev/null)" &&
+	   head="$(git rev-parse --verify HEAD 2>/dev/null)"; then
+		# If we are at a tagged commit, we ignore it.
+		if [ -z "$(git describe --exact-match 2>/dev/null)" ]; then
+			# Add -g and 8 hex chars.
+			printf '%s%s' -g "$(echo $head | cut -c1-8)"
+		fi
+		# Check for uncommitted changes.
+		# This script must avoid any write attempt to the source tree,
+		# which might be read-only.
+		# You cannot use 'git describe --dirty' because it tries to
+		# create .git/index.lock .
+		# First, with git-status, but --no-optional-locks is only
+		# supported in git >= 2.14, so fall back to git-diff-index if
+		# it fails. Note that git-diff-index does not refresh the
+		# index, so it may give misleading results. See
+		# git-update-index(1), git-diff-index(1), and git-status(1).
+		if {
+			git --no-optional-locks status -uno --porcelain 2>/dev/null ||
+			git diff-index --name-only HEAD
+		} | read dummy; then
+			printf '%s' -dirty
+		fi
+	fi
+}
+
+echo $(sed -n '1p' VERSION | tr -d '\n')$(scm_version)
-- 
2.20.1