Merge branch 'en/header-split-cleanup'

Split key function and data structure definitions out of cache.h to
new header files and adjust the users.

* en/header-split-cleanup:
  csum-file.h: remove unnecessary inclusion of cache.h
  write-or-die.h: move declarations for write-or-die.c functions from cache.h
  treewide: remove cache.h inclusion due to setup.h changes
  setup.h: move declarations for setup.c functions from cache.h
  treewide: remove cache.h inclusion due to environment.h changes
  environment.h: move declarations for environment.c functions from cache.h
  treewide: remove unnecessary includes of cache.h
  wrapper.h: move declarations for wrapper.c functions from cache.h
  path.h: move function declarations for path.c functions from cache.h
  cache.h: remove expand_user_path()
  abspath.h: move absolute path functions from cache.h
  environment: move comment_line_char from cache.h
  treewide: remove unnecessary cache.h inclusion from several sources
  treewide: remove unnecessary inclusion of gettext.h
  treewide: be explicit about dependence on gettext.h
  treewide: remove unnecessary cache.h inclusion from a few headers

submodule.c

@@ -1,4 +1,5 @@
-#include "git-compat-util.h"
+#include "cache.h"
+#include "abspath.h"
 #include "alloc.h"
 #include "repository.h"
 #include "config.h"
@@ -7,6 +8,8 @@
 #include "dir.h"
 #include "diff.h"
 #include "commit.h"
+#include "environment.h"
+#include "gettext.h"
 #include "hex.h"
 #include "revision.h"
 #include "run-command.h"
@@ -23,6 +26,7 @@
 #include "parse-options.h"
 #include "object-store.h"
 #include "commit-reach.h"
+#include "setup.h"
 #include "shallow.h"
 
 static int config_update_recurse_submodules = RECURSE_SUBMODULES_OFF;