meson: move headers definition from 'contrib/coccinelle'

The Meson build for coccinelle static analysis lists all headers to
analyse. Due to the way Meson exports variables between subdirs, this
variable is also available in the root Meson build.

An upcoming commit, will add a new check complimenting 'hdr-check' in
the Makefile. This would require the list of headers. So move the
'coccinelle_headers' to the root Meson build and rename it to 'headers',
remove the root path being appended to each header and retain that in
the coccinelle Meson build since it is specific to the coccinelle build.

Also move the 'third_party_sources' variable to the root Meson build
since it is also a dependency for the 'headers' variable. This also
makes it easier to understand as the variable is now propagated from the
top level to the bottom.

While 'headers_to_check' is only computed when we have a repository and
the 'git' executable is present, the variable itself is exposed as an
empty array. This allows dependencies in upcoming commits to simply
check for length of the array and not worry about dependencies required
to actually populate the array.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: KarthikNayak

contrib/coccinelle/meson.build

@@ -8,21 +8,6 @@ if not spatch.found()
   subdir_done()
 endif
 
-third_party_sources = [
-  ':!contrib',
-  ':!compat/inet_ntop.c',
-  ':!compat/inet_pton.c',
-  ':!compat/nedmalloc',
-  ':!compat/obstack.*',
-  ':!compat/poll',
-  ':!compat/regex',
-  ':!sha1collisiondetection',
-  ':!sha1dc',
-  ':!t/unit-tests/clar',
-  ':!t/unit-tests/clar',
-  ':!t/t[0-9][0-9][0-9][0-9]*',
-]
-
 rules = [
   'array.cocci',
   'commit.cocci',
@@ -61,7 +46,7 @@ foreach source : run_command(git, '-C', meson.project_source_root(), 'ls-files',
 endforeach
 
 coccinelle_headers = []
-foreach header : run_command(git, '-C', meson.project_source_root(), 'ls-files', '--deduplicate', '*.h', third_party_sources, check: true).stdout().split()
+foreach header : headers_to_check
   coccinelle_headers += meson.project_source_root() / header
 endforeach
 

meson.build

@@ -633,6 +633,28 @@ builtin_sources = [
   'builtin/write-tree.c',
 ]
 
+third_party_sources = [
+  ':!contrib',
+  ':!compat/inet_ntop.c',
+  ':!compat/inet_pton.c',
+  ':!compat/nedmalloc',
+  ':!compat/obstack.*',
+  ':!compat/poll',
+  ':!compat/regex',
+  ':!sha1collisiondetection',
+  ':!sha1dc',
+  ':!t/unit-tests/clar',
+  ':!t/unit-tests/clar',
+  ':!t/t[0-9][0-9][0-9][0-9]*',
+]
+
+headers_to_check = []
+if git.found() and fs.exists(meson.project_source_root() / '.git')
+  foreach header : run_command(git, '-C', meson.project_source_root(), 'ls-files', '--deduplicate', '*.h', third_party_sources, check: true).stdout().split()
+    headers_to_check += header
+  endforeach
+endif
+
 if not get_option('breaking_changes')
   builtin_sources += 'builtin/pack-redundant.c'
 endif