Merge branch 'jt/subprocess-handshake' into maint

Code cleanup.

* jt/subprocess-handshake:
sub-process: refactor handshake to common function
Documentation: migrate sub-process docs to header
convert: add "status=delayed" to filter process protocol
convert: refactor capabilities negotiation
convert: move multiple file filter error handling to separate function
convert: put the flags field before the flag itself for consistent style
t0021: write "OUT <size>" only on success
t0021: make debug log file name configurable
t0021: keep filter log files on comparison

diff --combined cache.h
index a09a5017fb940a72f7a9a08c6652563b8651f2a8,0625c49c85686fbb4dcaeee035614aee4e9eb4d4..25c98b68093858e5ffc37fd33cf2efb0b2561ba7
--- 1/cache.h
--- 2/cache.h
+++ b/cache.h
@@@ -1146,14 -1146,6 +1146,14 @@@ char *strip_path_suffix(const char *pat
  int daemon_avoid_alias(const char *path);
  extern int is_ntfs_dotgit(const char *name);
  
 +/*
 + * Returns true iff "str" could be confused as a command-line option when
 + * passed to a sub-program like "ssh". Note that this has nothing to do with
 + * shell-quoting, which should be handled separately; we're assuming here that
 + * the string makes it verbatim to the sub-program.
 + */
 +int looks_like_command_line_option(const char *str);
 +
  /**
   * Return a newly allocated string with the evaluation of
   * "$XDG_CONFIG_HOME/git/$filename" if $XDG_CONFIG_HOME is non-empty, otherwise
@@@ -1500,6 -1492,7 +1500,7 @@@ struct checkout 
        struct index_state *istate;
        const char *base_dir;
        int base_dir_len;
+       struct delayed_checkout *delayed_checkout;
        unsigned force:1,
                 quiet:1,
                 not_new:1,
@@@ -1509,6 -1502,8 +1510,8 @@@
  
  #define TEMPORARY_FILENAME_LENGTH 25
  extern int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath);
+ extern void enable_delayed_checkout(struct checkout *state);
+ extern int finish_delayed_checkout(struct checkout *state);
  
  struct cache_def {
        struct strbuf path;