Merge branch 'maint'

* maint:
git-bisect: make "start", "good" and "skip" succeed or fail atomically
git-am: cope better with an empty Subject: line
Ignore leading empty lines while summarizing merges
bisect: squelch "fatal: ref HEAD not a symref" misleading message
builtin-apply: Show a more descriptive error on failure when opening a patch
Clarify documentation of git-cvsserver, particularly in relation to git-shell

diff --combined builtin-apply.c
index c8ca41b68f8febb4856e3d6cc9a0ebef0a0a9973,30d26e57b30821d6b11efe4f493da6d35fb1dc18..caa3f2aa0ca147091d28013c3d2c11346e350675
--- 1/builtin-apply.c
--- 2/builtin-apply.c
+++ b/builtin-apply.c
@@@ -2981,8 -2981,12 +2981,8 @@@ static int apply_patch(int fd, const ch
  
  static int git_apply_config(const char *var, const char *value)
  {
 -      if (!strcmp(var, "apply.whitespace")) {
 -              if (!value)
 -                      return config_error_nonbool(var);
 -              apply_default_whitespace = xstrdup(value);
 -              return 0;
 -      }
 +      if (!strcmp(var, "apply.whitespace"))
 +              return git_config_string(&apply_default_whitespace, var, value);
        return git_default_config(var, value);
  }
  
@@@ -3117,7 -3121,7 +3117,7 @@@ int cmd_apply(int argc, const char **ar
  
                fd = open(arg, O_RDONLY);
                if (fd < 0)
-                       usage(apply_usage);
+                       die("can't open patch '%s': %s", arg, strerror(errno));
                read_stdin = 0;
                set_default_whitespace_mode(whitespace_option);
                errs |= apply_patch(fd, arg, inaccurate_eof);

diff --combined git-bisect.sh
index 408775a51e2ad7b3007ea8a0001516c26166318a,8e57e9a75dd9916d2c5a59f224859d1a22854c7f..d8d9bfde4cdd4b558992c68cb7cdaaa1b8a1212d
--- 1/git-bisect.sh
--- 2/git-bisect.sh
+++ b/git-bisect.sh
@@@ -1,9 -1,7 +1,9 @@@
  #!/bin/sh
  
 -USAGE='[start|bad|good|skip|next|reset|visualize|replay|log|run]'
 -LONG_USAGE='git bisect start [<bad> [<good>...]] [--] [<pathspec>...]
 +USAGE='[help|start|bad|good|skip|next|reset|visualize|replay|log|run]'
 +LONG_USAGE='git bisect help
 +        print this long help message.
 +git bisect start [<bad> [<good>...]] [--] [<pathspec>...]
          reset bisect state and start bisection.
  git bisect bad [<rev>]
          mark <rev> a known-bad revision.
@@@ -22,9 -20,7 +22,9 @@@ git bisect replay <logfile
  git bisect log
          show bisect log.
  git bisect run <cmd>...
 -        use <cmd>... to automatically bisect.'
 +        use <cmd>... to automatically bisect.
 +
 +Please use "git help bisect" to get the full man page.'
  
  OPTIONS_SPEC=
  . git-sh-setup
@@@ -66,9 -62,10 +66,10 @@@ bisect_start() 
        # Verify HEAD. If we were bisecting before this, reset to the
        # top-of-line master first!
        #
-       head=$(GIT_DIR="$GIT_DIR" git symbolic-ref HEAD) ||
+       head=$(GIT_DIR="$GIT_DIR" git symbolic-ref -q HEAD) ||
        head=$(GIT_DIR="$GIT_DIR" git rev-parse --verify HEAD) ||
        die "Bad HEAD - I need a HEAD"
+       start_head=''
        case "$head" in
        refs/heads/bisect)
                if [ -s "$GIT_DIR/BISECT_START" ]; then
@@@ -82,7 -79,7 +83,7 @@@
                # This error message should only be triggered by cogito usage,
                # and cogito users should understand it relates to cg-seek.
                [ -s "$GIT_DIR/head-name" ] && die "won't bisect on seeked tree"
-               echo "${head#refs/heads/}" >"$GIT_DIR/BISECT_START"
+               start_head="${head#refs/heads/}"
                ;;
        *)
                die "Bad HEAD - strange symbolic ref"
@@@ -103,6 -100,7 +104,7 @@@
        done
        orig_args=$(sq "$@")
        bad_seen=0
+       eval=''
        while [ $# -gt 0 ]; do
            arg="$1"
            case "$arg" in
@@@ -120,13 -118,15 +122,15 @@@
                0) state='bad' ; bad_seen=1 ;;
                *) state='good' ;;
                esac
-               bisect_write "$state" "$rev" 'nolog'
+               eval="$eval bisect_write '$state' '$rev' 'nolog'; "
                shift
                ;;
            esac
        done
  
        sq "$@" >"$GIT_DIR/BISECT_NAMES"
+       test -n "$start_head" && echo "$start_head" >"$GIT_DIR/BISECT_START"
+       eval "$eval"
        echo "git-bisect start$orig_args" >>"$GIT_DIR/BISECT_LOG"
        bisect_auto_next
  }
@@@ -157,12 -157,14 +161,14 @@@ bisect_state() 
                bisect_write "$state" "$rev" ;;
        2,bad|*,good|*,skip)
                shift
+               eval=''
                for rev in "$@"
                do
                        sha=$(git rev-parse --verify "$rev^{commit}") ||
                                die "Bad rev input: $rev"
-                       bisect_write "$state" "$sha"
-               done ;;
+                       eval="$eval bisect_write '$state' '$sha'; "
+               done
+               eval "$eval" ;;
        *,bad)
                die "'git bisect bad' can take only one argument." ;;
        *)
@@@ -465,8 -467,6 +471,8 @@@ case "$#" i
      cmd="$1"
      shift
      case "$cmd" in
 +    help)
 +        git bisect -h ;;
      start)
          bisect_start "$@" ;;
      bad|good|skip)