git: 16354ca2d8c4 - stable/12 - newvers.sh: avoid regenerating vers.c if content unchanged

The branch stable/12 has been updated by emaste:

URL: https://cgit.FreeBSD.org/src/commit/?id=16354ca2d8c45e2e72bffbb61d99f5fe3858b6de

commit 16354ca2d8c45e2e72bffbb61d99f5fe3858b6de
Author:     Ed Maste <emaste@FreeBSD.org>
AuthorDate: 2018-11-07 20:36:57 +0000
Commit:     Ed Maste <emaste@FreeBSD.org>
CommitDate: 2022-09-06 19:11:09 +0000

    newvers.sh: avoid regenerating vers.c if content unchanged
    
    When reproducible build mode is enabled vers.c may be unchanged between
    successive builds.  In this case avoid changing the file's metadata so
    that it does not cause dependent targets to be rebuilt.
    
    Sponsored by:   The FreeBSD Foundation
    Reviewed by:    imp
    Differential Revision:  https://reviews.freebsd.org/D17892
    
    (cherry picked from commit 179460e1481ef98aa6824681ee472b0764c9d9a0)
---
 sys/conf/newvers.sh | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/sys/conf/newvers.sh b/sys/conf/newvers.sh
index 18ada43e0cbc..542dae42b567 100644
--- a/sys/conf/newvers.sh
+++ b/sys/conf/newvers.sh
@@ -285,7 +285,7 @@ else
 	VERSTR="${VERINFO}\\n    ${u}@${h}:${d}\\n"
 fi
 
-cat << EOF > vers.c
+vers_content_new=$(cat << EOF
 $COPYRIGHT
 #define SCCSSTR "@(#)${VERINFO}"
 #define VERSTR "${VERSTR}"
@@ -299,5 +299,10 @@ char osrelease[sizeof(RELSTR) > 32 ? sizeof(RELSTR) : 32] = RELSTR;
 int osreldate = ${RELDATE};
 char kern_ident[] = "${i}";
 EOF
+)
+vers_content_old=$(cat vers.c 2>/dev/null || true)
+if [ "$vers_content_new" != "$vers_content_old" ]; then
+	echo "$vers_content_new" > vers.c
+fi
 
 echo $((v + 1)) > version