Merge branch 'cc/apply-am'

"git am" has been taught to make an internal call to "git apply"'s
innards without spawning the latter as a separate process.

* cc/apply-am: (41 commits)
  builtin/am: use apply API in run_apply()
  apply: learn to use a different index file
  apply: pass apply state to build_fake_ancestor()
  apply: refactor `git apply` option parsing
  apply: change error_routine when silent
  usage: add get_error_routine() and get_warn_routine()
  usage: add set_warn_routine()
  apply: don't print on stdout in verbosity_silent mode
  apply: make it possible to silently apply
  apply: use error_errno() where possible
  apply: make some parsing functions static again
  apply: move libified code from builtin/apply.c to apply.{c,h}
  apply: rename and move opt constants to apply.h
  builtin/apply: rename option parsing functions
  builtin/apply: make create_one_file() return -1 on error
  builtin/apply: make try_create_file() return -1 on error
  builtin/apply: make write_out_results() return -1 on error
  builtin/apply: make write_out_one_result() return -1 on error
  builtin/apply: make create_file() return -1 on error
  builtin/apply: make add_index_file() return -1 on error
  ...

usage.c

@@ -70,6 +70,21 @@ void set_error_routine(void (*routine)(const char *err, va_list params))
 	error_routine = routine;
 }
 
+void (*get_error_routine(void))(const char *err, va_list params)
+{
+	return error_routine;
+}
+
+void set_warn_routine(void (*routine)(const char *warn, va_list params))
+{
+	warn_routine = routine;
+}
+
+void (*get_warn_routine(void))(const char *warn, va_list params)
+{
+	return warn_routine;
+}
+
 void set_die_is_recursing_routine(int (*routine)(void))
 {
 	die_is_recursing = routine;