[PATCH v2] perf tools: Fix empty version number when building outside of a git repo

[Will Chandler]

When perf is built in a full source tree that is not a git repository,
e.g. from a kernel source tarball, `perf version` will print empty tag
and commit strings:

  $ perf version
  perf version

Currently the tag version is only generated from the root Makefile when
building in a git repository. If PERF-VERSION-FILE has not been
generated and the source tree is not in a git repository, then
PERF-VERSION-GEN will return an empty version.

The problem can be reproduced with the following steps:

  $ wget https://git.kernel.org/torvalds/t/linux-6.0-rc7.tar.gz
  $ tar -xf linux-6.0-rc7.tar.gz && cd linux-6.0-rc7
  $ make -C tools/perf
  $ tools/perf/perf -v
  perf version

Builds from tarballs generated with `make perf-tar-src-pkg` are not
impacted by this issue as PERF-VERSION-FILE is included in the archive.

The perf RPM provided by Fedora for 5.18+ is experiencing this problem.
Package build logs[0] show that the build is attempting to fall back on
PERF-VERSION-FILE, but it is not present.

To resolve this, revert back to the previous logic of using the kernel
Makefile version if not in a git repository and PERF-VERSION-FILE does
not exist.

[0] https://kojipkgs.fedoraproject.org/packages/kernel-tools/5.19.4/200.fc36/data/logs/x86_64/build.log

Fixes: 7572733b8499 ("perf tools: Fix version kernel tag, 2022-02-21")
Signed-off-by: Will Chandler <wfc@xxxxxxxxxxxxxx>
---
Range-diff against v1:
1:  8195a5ccd82d < -:  ------------ perf tools: Fix empty version number when building outside of a git repo
-:  ------------ > 1:  a3beccdab700 perf tools: Fix empty version number when building outside of a git repo

 tools/perf/util/PERF-VERSION-GEN | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/PERF-VERSION-GEN b/tools/perf/util/PERF-VERSION-GEN
index 0ee5af529238..3cc42821d9b3 100755
--- a/tools/perf/util/PERF-VERSION-GEN
+++ b/tools/perf/util/PERF-VERSION-GEN
@@ -11,7 +11,8 @@ LF='
 '
 
 #
-# Always try first to get the version from the kernel Makefile
+# Use version from kernel Makefile unless not in a git repository and
+# PERF-VERSION-FILE exists
 #
 CID=
 TAG=
@@ -19,9 +20,14 @@ if test -d ../../.git -o -f ../../.git
 then
 	TAG=$(MAKEFLAGS= make -sC ../.. kernelversion)
 	CID=$(git log -1 --abbrev=12 --pretty=format:"%h" 2>/dev/null) && CID="-g$CID"
-else
+elif test -f ../../PERF-VERSION-FILE
+then
 	TAG=$(cut -d' ' -f3 ../../PERF-VERSION-FILE | sed -e 's/\"//g')
 fi
+if test -z "$TAG"
+then
+	TAG=$(MAKEFLAGS= make -sC ../.. kernelversion)
+fi
 
 VN="$TAG$CID"
 if test -n "$CID"
-- 
2.37.3