[PATCH] perf tools: Fix check-headers.sh AND list path of execution

[Alexander Kapshuk <alexander.kapshuk@gmail.com>]

The '||' path of execution in the 'test' block of the check_2() function
may also be taken if file2 does not exist, in which case the warning
message about the ABI headers being different would still be printed
where it should not be.  See below.

% file1=file1; file2=file2
% cmd="echo diff $file1 $file2"
% test -f $file2 &&
eval $cmd || echo "Warning: Kernel ABI header at 'tools/$file1'
differs from latest version at '$file2'" >&2
Warning: Kernel ABI header at 'tools/file1' differs from latest
version at 'file2'

The proposed patch converts the code following the '&&' operator into a
compound list to be executed in the current process environment only if
file2 does exist. Should the files being compared differ, a diff command
to compare the files concerned is printed on standard output. E.g.

diff -u tools/arch/x86/lib/memcpy_64.S arch/x86/lib/memcpy_64.S

Signed-off-by: Alexander Kapshuk <alexander.kapshuk@gmail.com>
---
 tools/perf/check-headers.sh | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh
index de28466c0186..ea48aa6f8d19 100755
--- a/tools/perf/check-headers.sh
+++ b/tools/perf/check-headers.sh
@@ -67,8 +67,12 @@ check_2 () {
 
   cmd="diff $* $file1 $file2 > /dev/null"
 
-  test -f $file2 &&
-  eval $cmd || echo "Warning: Kernel ABI header at 'tools/$file' differs from latest version at '$file'" >&2
+  test -f $file2 && {
+    eval $cmd || {
+      echo "Warning: Kernel ABI header at 'tools/$file' differs from latest version at '$file'" >&2
+      echo diff -u tools/$file $file
+    }
+  }
 }
 
 check () {
-- 
2.18.0