fortran: make include scanning also work for CMake subprojects

also fixed PEP8

I originally implemented the "include" scanning,
but hadn't made a test for this case

mesonbuild/backend/ninjabackend.py

@@ -543,10 +543,10 @@ int dummy;
         # rule store as being wanted in compdb
         for for_machine in MachineChoice:
             for lang in self.environment.coredata.compilers[for_machine]:
-                rules += [ "%s%s" % (rule, ext) for rule in [self.get_compiler_rule_name(lang, for_machine)]
-                                                for ext in ['', '_RSP']]
-                rules += [ "%s%s" % (rule, ext) for rule in [self.get_pch_rule_name(lang, for_machine)]
-                                                for ext in ['', '_RSP']]
+                rules += ["%s%s" % (rule, ext) for rule in [self.get_compiler_rule_name(lang, for_machine)]
+                          for ext in ['', '_RSP']]
+                rules += ["%s%s" % (rule, ext) for rule in [self.get_pch_rule_name(lang, for_machine)]
+                          for ext in ['', '_RSP']]
         compdb_options = ['-x'] if mesonlib.version_compare(self.ninja_version, '>=1.9') else []
         ninja_compdb = [self.ninja_command, '-t', 'compdb'] + compdb_options + rules
         builddir = self.environment.get_build_dir()
@@ -990,7 +990,7 @@ int dummy;
                                     self.build.get_subproject_dir()),
                        self.environment.get_build_dir(),
                        self.environment.get_log_dir()] +
-                       (['--use_llvm_cov'] if use_llvm_cov else []))
+                      (['--use_llvm_cov'] if use_llvm_cov else []))
 
     def generate_coverage_rules(self):
         e = NinjaBuildElement(self.all_outputs, 'meson-coverage', 'CUSTOM_COMMAND', 'PHONY')
@@ -1560,13 +1560,13 @@ int dummy;
                                                                self.get_target_dir(target))
             else:
                 target_slashname_workaround_dir = self.get_target_dir(target)
-            (rpath_args, target.rpath_dirs_to_remove) = \
-                         rustc.build_rpath_args(self.environment,
-                                                self.environment.get_build_dir(),
-                                                target_slashname_workaround_dir,
-                                                self.determine_rpath_dirs(target),
-                                                target.build_rpath,
-                                                target.install_rpath)
+            rpath_args, target.rpath_dirs_to_remove = (
+                rustc.build_rpath_args(self.environment,
+                                       self.environment.get_build_dir(),
+                                       target_slashname_workaround_dir,
+                                       self.determine_rpath_dirs(target),
+                                       target.build_rpath,
+                                       target.install_rpath))
             # ... but then add rustc's sysroot to account for rustup
             # installations
             for rpath_arg in rpath_args:
@@ -2777,13 +2777,13 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
                 self.get_target_dir(target))
         else:
             target_slashname_workaround_dir = self.get_target_dir(target)
-        (rpath_args, target.rpath_dirs_to_remove) = \
-                    linker.build_rpath_args(self.environment,
-                                            self.environment.get_build_dir(),
-                                            target_slashname_workaround_dir,
-                                            self.determine_rpath_dirs(target),
-                                            target.build_rpath,
-                                            target.install_rpath)
+        (rpath_args, target.rpath_dirs_to_remove) = (
+            linker.build_rpath_args(self.environment,
+                                    self.environment.get_build_dir(),
+                                    target_slashname_workaround_dir,
+                                    self.determine_rpath_dirs(target),
+                                    target.build_rpath,
+                                    target.install_rpath))
         commands += rpath_args
         # Add libraries generated by custom targets
         custom_target_libraries = self.get_custom_target_provided_libraries(target)
@@ -3041,7 +3041,9 @@ def _scan_fortran_file_deps(src: Path, srcdir: Path, dirname: Path, tdeps, compi
             # included files
             incmatch = incre.match(line)
             if incmatch is not None:
-                incfile = srcdir / incmatch.group(1)
+                incfile = src.parent / incmatch.group(1)
+                # NOTE: src.parent is most general, in particular for CMake subproject with Fortran file
+                # having an `include 'foo.f'` statement.
                 if incfile.suffix.lower()[1:] in compiler.file_suffixes:
                     mod_files.extend(_scan_fortran_file_deps(incfile, srcdir, dirname, tdeps, compiler))
             # modules