contrib/coccinelle: pass include paths to spatch(1)

In the previous commit a new coccinelle rule is added. But neiter
`make coccicheck` nor `meson compile coccicheck` did detect a case in
builtin/last-modified.c.

This case involves the field `scratch` in `struct last_modified`. This
field is of type `struct bitmap` and that struct has a member
`eword_t *words`. Both are defined in `ewah/ewok.h`. Now, while
builtin/last-modified.c does include that header (with the subdir in the
#include directive), it seems coccinelle does not process it. So it's
unaware of the type of `words` in the bitmap, and it doesn't recognize
the rule from previous commit that uses:

    type T;
    T *ptr;

Fix coccicheck by passing all possible include paths inside the Git
project so spatch(1) can find the headers and can determine the types.

Signed-off-by: Toon Claes <toon@iotcl.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: To1ne

Makefile

@@ -981,7 +981,7 @@ SANITIZE_LEAK =
 SANITIZE_ADDRESS =
 
 # For the 'coccicheck' target
-SPATCH_INCLUDE_FLAGS = --all-includes
+SPATCH_INCLUDE_FLAGS = --all-includes $(addprefix -I ,compat ewah refs sha256 trace2 win32 xdiff)
 SPATCH_FLAGS =
 SPATCH_TEST_FLAGS =
 

contrib/coccinelle/meson.build

@@ -50,6 +50,11 @@ foreach header : headers_to_check
   coccinelle_headers += meson.project_source_root() / header
 endforeach
 
+coccinelle_includes = []
+foreach path : ['compat', 'ewah', 'refs', 'sha256', 'trace2', 'win32', 'xdiff']
+  coccinelle_includes += ['-I', meson.project_source_root() / path]
+endforeach
+
 patches = [ ]
 foreach source : coccinelle_sources
   patches += custom_target(
@@ -58,6 +63,7 @@ foreach source : coccinelle_sources
       '--all-includes',
       '--sp-file', concatenated_rules,
       '--patch', meson.project_source_root(),
+      coccinelle_includes,
       '@INPUT@',
     ],
     input: meson.project_source_root() / source,