Documentation: migrate sub-process docs to header

Move the documentation for the sub-process API from a separate txt file
to its header file.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-sub-process.txt

@@ -1,59 +0,0 @@
-sub-process API
-===============
-
-The sub-process API makes it possible to run background sub-processes
-for the entire lifetime of a Git invocation. If Git needs to communicate
-with an external process multiple times, then this can reduces the process
-invocation overhead. Git and the sub-process communicate through stdin and
-stdout.
-
-The sub-processes are kept in a hashmap by command name and looked up
-via the subprocess_find_entry function.  If an existing instance can not
-be found then a new process should be created and started.  When the
-parent git command terminates, all sub-processes are also terminated.
-
-This API is based on the run-command API.
-
-Data structures
----------------
-
-* `struct subprocess_entry`
-
-The sub-process structure.  Members should not be accessed directly.
-
-Types
------
-
-'int(*subprocess_start_fn)(struct subprocess_entry *entry)'::
-
-	User-supplied function to initialize the sub-process.  This is
-	typically used to negotiate the interface version and capabilities.
-
-
-Functions
----------
-
-`cmd2process_cmp`::
-
-	Function to test two subprocess hashmap entries for equality.
-
-`subprocess_start`::
-
-	Start a subprocess and add it to the subprocess hashmap.
-
-`subprocess_stop`::
-
-	Kill a subprocess and remove it from the subprocess hashmap.
-
-`subprocess_find_entry`::
-
-	Find a subprocess in the subprocess hashmap.
-
-`subprocess_get_child_process`::
-
-	Get the underlying `struct child_process` from a subprocess.
-
-`subprocess_read_status`::
-
-	Helper function to read packets looking for the last "status=<foo>"
-	key/value pair.

sub-process.h

@@ -6,12 +6,23 @@
 #include "run-command.h"
 
 /*
- * Generic implementation of background process infrastructure.
+ * The sub-process API makes it possible to run background sub-processes
- * See: Documentation/technical/api-sub-process.txt
+ * for the entire lifetime of a Git invocation. If Git needs to communicate
+ * with an external process multiple times, then this can reduces the process
+ * invocation overhead. Git and the sub-process communicate through stdin and
+ * stdout.
+ *
+ * The sub-processes are kept in a hashmap by command name and looked up
+ * via the subprocess_find_entry function.  If an existing instance can not
+ * be found then a new process should be created and started.  When the
+ * parent git command terminates, all sub-processes are also terminated.
+ *
+ * This API is based on the run-command API.
  */
 
  /* data structures */
 
+/* Members should not be accessed directly. */
 struct subprocess_entry {
 	struct hashmap_entry ent; /* must be the first member! */
 	const char *cmd;
@@ -20,21 +31,31 @@ struct subprocess_entry {
 
 /* subprocess functions */
 
+/* Function to test two subprocess hashmap entries for equality. */
 extern int cmd2process_cmp(const void *unused_cmp_data,
 			   const struct subprocess_entry *e1,
 			   const struct subprocess_entry *e2,
 			   const void *unused_keydata);
 
+/*
+ * User-supplied function to initialize the sub-process.  This is
+ * typically used to negotiate the interface version and capabilities.
+ */
 typedef int(*subprocess_start_fn)(struct subprocess_entry *entry);
+
+/* Start a subprocess and add it to the subprocess hashmap. */
 int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, const char *cmd,
 		subprocess_start_fn startfn);
 
+/* Kill a subprocess and remove it from the subprocess hashmap. */
 void subprocess_stop(struct hashmap *hashmap, struct subprocess_entry *entry);
 
+/* Find a subprocess in the subprocess hashmap. */
 struct subprocess_entry *subprocess_find_entry(struct hashmap *hashmap, const char *cmd);
 
 /* subprocess helper functions */
 
+/* Get the underlying `struct child_process` from a subprocess. */
 static inline struct child_process *subprocess_get_child_process(
 		struct subprocess_entry *entry)
 {