parse-options: show negatability of options in short help

Add a "[no-]" prefix to options without the flag PARSE_OPT_NONEG to
document the fact that you can negate them.

This looks a bit strange for options that already start with "no-", e.g.
for the option --no-name of git show-branch:

    --[no-]no-name        suppress naming strings

You can actually use --no-no-name as an alias of --name, so the short
help is not wrong.  If we strip off any of the "no-"s, we lose either
the ability to see if the remaining one belongs to the documented
variant or to see if it can be negated.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rev-parse.txt

@@ -424,10 +424,10 @@ usage: some-command [<options>] <args>...
     some-command does foo and bar!
 
     -h, --help            show the help
-    --foo                 some nifty option --foo
+    --[no-]foo            some nifty option --foo
-    --bar ...             some cool option --bar with an argument
+    --[no-]bar ...        some cool option --bar with an argument
-    --baz <arg>           another cool option --baz with a named argument
+    --[no-]baz <arg>      another cool option --baz with a named argument
-    --qux[=<path>]        qux may take a path argument but has meaning by itself
+    --[no-]qux[=<path>]   qux may take a path argument but has meaning by itself
 
 An option group Header
     -C[...]               option C with an optional argument

contrib/subtree/t/t7900-subtree.sh

@@ -71,7 +71,7 @@ test_expect_success 'shows short help text for -h' '
 	test_expect_code 129 git subtree -h >out 2>err &&
 	test_must_be_empty err &&
 	grep -e "^ *or: git subtree pull" out &&
-	grep -e --annotate out
+	grep -F -e "--[no-]annotate" out
 '
 
 #

parse-options.c

@@ -1137,8 +1137,14 @@ static enum parse_opt_result usage_with_options_internal(struct parse_opt_ctx_t
 		}
 		if (opts->long_name && opts->short_name)
 			pos += fprintf(outfile, ", ");
-		if (opts->long_name)
+		if (opts->long_name) {
-			pos += fprintf(outfile, "--%s", opts->long_name);
+			const char *long_name = opts->long_name;
+			if (opts->flags & PARSE_OPT_NONEG)
+				pos += fprintf(outfile, "--%s", long_name);
+			else
+				pos += fprintf(outfile, "--[no-]%s", long_name);
+		}
+
 		if (opts->type == OPTION_NUMBER)
 			pos += utf8_fprintf(outfile, _("-NUM"));
 

t/t0040-parse-options.sh

@@ -13,30 +13,34 @@ usage: test-tool parse-options <options>
 
     A helper function for the parse-options API.
 
-    --yes                 get a boolean
+    --[no-]yes            get a boolean
-    -D, --no-doubt        begins with 'no-'
+    -D, --[no-]no-doubt   begins with 'no-'
     -B, --no-fear         be brave
-    -b, --boolean         increment by one
+    -b, --[no-]boolean    increment by one
-    -4, --or4             bitwise-or boolean with ...0100
+    -4, --[no-]or4        bitwise-or boolean with ...0100
-    --neg-or4             same as --no-or4
+    --[no-]neg-or4        same as --no-or4
 
-    -i, --integer <n>     get a integer
+    -i, --[no-]integer <n>
+                          get a integer
     -j <n>                get a integer, too
     -m, --magnitude <n>   get a magnitude
-    --set23               set integer to 23
+    --[no-]set23          set integer to 23
     --mode1               set integer to 1 (cmdmode option)
     --mode2               set integer to 2 (cmdmode option)
-    -L, --length <str>    get length of <str>
+    -L, --[no-]length <str>
-    -F, --file <file>     set file to <file>
+                          get length of <str>
+    -F, --[no-]file <file>
+                          set file to <file>
 
 String options
-    -s, --string <string> get a string
+    -s, --[no-]string <string>
-    --string2 <str>       get another string
+                          get a string
-    --st <st>             get another string (pervert ordering)
+    --[no-]string2 <str>  get another string
+    --[no-]st <st>        get another string (pervert ordering)
     -o <str>              get another string
     --longhelp            help text of this entry
                           spans multiple lines
-    --list <str>          add str to list
+    --[no-]list <str>     add str to list
 
 Magic arguments
     -NUM                  set integer to NUM
@@ -45,16 +49,17 @@ Magic arguments
     --no-ambiguous        negative ambiguity
 
 Standard options
-    --abbrev[=<n>]        use <n> digits to display object names
+    --[no-]abbrev[=<n>]   use <n> digits to display object names
-    -v, --verbose         be verbose
+    -v, --[no-]verbose    be verbose
-    -n, --dry-run         dry run
+    -n, --[no-]dry-run    dry run
-    -q, --quiet           be quiet
+    -q, --[no-]quiet      be quiet
-    --expect <string>     expected output in the variable dump
+    --[no-]expect <string>
+                          expected output in the variable dump
 
 Alias
-    -A, --alias-source <string>
+    -A, --[no-]alias-source <string>
                           get a string
-    -Z, --alias-target <string>
+    -Z, --[no-]alias-target <string>
                           alias of --alias-source
 
 EOF

t/t1502-rev-parse-parseopt.sh

@@ -111,7 +111,7 @@ test_expect_success 'test --parseopt help-all output hidden switches' '
 |
 |    some-command does foo and bar!
 |
-|    --hidden1             A hidden switch
+|    --[no-]hidden1        A hidden switch
 |
 |EOF
 END_EXPECT

t/t1502/optionspec-neg.help

@@ -3,8 +3,8 @@ usage: some-command [options] <args>...
 
     some-command does foo and bar!
 
-    --foo                 can be negated
+    --[no-]foo            can be negated
-    --no-bar              can be positivated
+    --[no-]no-bar         can be positivated
     --positive-only       cannot be negated
     --no-negative         cannot be positivated
 

t/t1502/optionspec.help

@@ -4,31 +4,33 @@ usage: some-command [options] <args>...
     some-command does foo and bar!
 
     -h, --help            show the help
-    --foo                 some nifty option --foo
+    --[no-]foo            some nifty option --foo
-    --bar ...             some cool option --bar with an argument
+    --[no-]bar ...        some cool option --bar with an argument
-    -b, --baz             a short and long option
+    -b, --[no-]baz        a short and long option
 
 An option group Header
     -C[...]               option C with an optional argument
-    -d, --data[=...]      short and long option with an optional argument
+    -d, --[no-]data[=...] short and long option with an optional argument
 
 Argument hints
     -B <arg>              short option required argument
-    --bar2 <arg>          long option required argument
+    --[no-]bar2 <arg>     long option required argument
-    -e, --fuz <with-space>
+    -e, --[no-]fuz <with-space>
                           short and long option required argument
     -s[<some>]            short option optional argument
-    --long[=<data>]       long option optional argument
+    --[no-]long[=<data>]  long option optional argument
-    -g, --fluf[=<path>]   short and long option optional argument
+    -g, --[no-]fluf[=<path>]
-    --longest <very-long-argument-hint>
+                          short and long option optional argument
+    --[no-]longest <very-long-argument-hint>
                           a very long argument hint
-    --pair <key=value>    with an equals sign in the hint
+    --[no-]pair <key=value>
-    --aswitch             help te=t contains? fl*g characters!`
+                          with an equals sign in the hint
-    --bswitch <hint>      hint has trailing tab character
+    --[no-]aswitch        help te=t contains? fl*g characters!`
-    --cswitch             switch has trailing tab character
+    --[no-]bswitch <hint> hint has trailing tab character
-    --short-hint <a>      with a one symbol hint
+    --[no-]cswitch        switch has trailing tab character
+    --[no-]short-hint <a> with a one symbol hint
 
 Extras
-    --extra1              line above used to cause a segfault but no longer does
+    --[no-]extra1         line above used to cause a segfault but no longer does
 
 EOF