2 files changed, 47 insertions, 3 deletions
diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt
index c5d141cd63..f6a4a361bd 100644
--- a/Documentation/technical/api-parse-options.txt
+++ b/Documentation/technical/api-parse-options.txt
@@ -118,13 +118,16 @@ There are some macros to easily define options:
 `OPT__COLOR(&int_var, description)`::
 	Add `\--color[=<when>]` and `--no-color`.
 
-`OPT__DRY_RUN(&int_var)`::
+`OPT__DRY_RUN(&int_var, description)`::
 	Add `-n, \--dry-run`.
 
-`OPT__QUIET(&int_var)`::
+`OPT__FORCE(&int_var, description)`::
+	Add `-f, \--force`.
+
+`OPT__QUIET(&int_var, description)`::
 	Add `-q, \--quiet`.
 
-`OPT__VERBOSE(&int_var)`::
+`OPT__VERBOSE(&int_var, description)`::
 	Add `-v, \--verbose`.
 
 `OPT_GROUP(description)`::
diff --git a/Documentation/technical/api-sigchain.txt b/Documentation/technical/api-sigchain.txt
new file mode 100644
index 0000000000..9e1189ef01
--- /dev/null
+++ b/Documentation/technical/api-sigchain.txt
@@ -0,0 +1,41 @@
+sigchain API
+============
+
+Code often wants to set a signal handler to clean up temporary files or
+other work-in-progress when we die unexpectedly. For multiple pieces of
+code to do this without conflicting, each piece of code must remember
+the old value of the handler and restore it either when:
+
+  1. The work-in-progress is finished, and the handler is no longer
+     necessary. The handler should revert to the original behavior
+     (either another handler, SIG_DFL, or SIG_IGN).
+
+  2. The signal is received. We should then do our cleanup, then chain
+     to the next handler (or die if it is SIG_DFL).
+
+Sigchain is a tiny library for keeping a stack of handlers. Your handler
+and installation code should look something like:
+
+------------------------------------------
+  void clean_foo_on_signal(int sig)
+  {
+	  clean_foo();
+	  sigchain_pop(sig);
+	  raise(sig);
+  }
+
+  void other_func()
+  {
+	  sigchain_push_common(clean_foo_on_signal);
+	  mess_up_foo();
+	  clean_foo();
+  }
+------------------------------------------
+
+Handlers are given the typedef of sigchain_fun. This is the same type
+that is given to signal() or sigaction(). It is perfectly reasonable to
+push SIG_DFL or SIG_IGN onto the stack.
+
+You can sigchain_push and sigchain_pop individual signals. For
+convenience, sigchain_push_common will push the handler onto the stack
+for many common signals.