On 3/4/2014 11:22 AM, Junio C Hamano wrote:
Ilya Bobyr <ilya.bo...@gmail.com> writes:

Built-in commands can specify names for option arguments, that are shown
when usage text is generated for the command.  sh based commands should
be able to do the same.

Option argument name hint is any text that comes after [*=?!] after the
argument name up to the first whitespace.  Underscores are replaced with
whitespace.  It is unlikely that an underscore would be useful in the
hint text.

Signed-off-by: Ilya Bobyr <ilya.bo...@gmail.com>
---
  Documentation/git-rev-parse.txt |   11 +++++++++--
  builtin/rev-parse.c             |   17 ++++++++++++++++-
  t/t1502-rev-parse-parseopt.sh   |   20 ++++++++++++++++++++
  3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 0d2cdcd..4cb6e02 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -284,13 +284,13 @@ Input Format
'git rev-parse --parseopt' input format is fully text based. It has two parts,
  separated by a line that contains only `--`. The lines before the separator
-(should be more than one) are used for the usage.
+(could be more than one) are used for the usage.
Good spotting.  I think the original author meant to say there
should be at least one line to serve as the usage string, so
updating it to "should be one or more" may be more accurate, but
"could be more than one" would also work.

Changed to "should be one or more".

  The lines after the separator describe the options.
Each line of options has this format: ------------
-<opt_spec><flags>* SP+ help LF
+<opt_spec><flags>*<argh>? SP+ help LF
  ------------
`<opt_spec>`::
@@ -313,6 +313,12 @@ Each line of options has this format:
* Use `!` to not make the corresponding negated long option available. +`<argh>`::
+       `<argh>`, if specified, is used as a name of the argument, if the
+       option takes an argument. `<argh>` is terminated by the first
+       whitespace. Angle braces are added automatically.  Underscore symbols
+       are replaced with spaces.
I had a hard time understanding this "Angle brackets are added
automatically" one (obviously nobody wants extra angle brackets
added around option arguments given by the user), until I looked at
the addition of the test to realize that this description is only
about how it appears in the help output.  The description needs to
be clarified to avoid confusion.

I've reworded some of the sentences. I think it is better now. Let me know what you think.

@@ -333,6 +339,7 @@ h,help    show the help
foo some nifty option --foo
  bar=      some cool option --bar with an argument
+baz=arg   another cool option --baz with an argument named <arg>
It probably is better not to have " named <arg>" at the end here, as
that gives an apparent-but-false contradiction with the "Angle
brackets are added *automatically*" and confuse readers.  At least,
it confused _this_ reader.

I am not sure I understand what is confusing here. But I removed the " named <arg>" part. If there would be an example, I think, it is easy to understand how it works.

After the "eval" in the existing example to parse the "$@" argument
list in this part of the documentation, it may be a good idea to say
something like:

        The above command, when "$@" is "--help", produces the
        following help output:

        ... sample output here ...

to show the actual output.  That way, we can illustrate how input
"baz?arg description of baz" is turned into "--baz[=<arg>]" output
clearly (yes, I am suggesting to use '?' in the new example, not '='
whose usage is already shown in the existing example).

Documentation on the whole argument parsing is quite short, so, I though, adding an example just to show how usage is generated would look like I am trying to make this feature look important than it is :)

I've added another section that shows usage text generated for the example specification.

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index aaeb611..83a769e 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -395,9 +395,10 @@ static int cmd_parseopt(int argc, const char **argv, const 
char *prefix)
                usage[unb++] = strbuf_detach(&sb, NULL);
        }
- /* parse: (<short>|<short>,<long>|<long>)[=?]? SP+ <help> */
+       /* parse: (<short>|<short>,<long>|<long>)[*=?!]*<arghint>? SP+ <help> */
        while (strbuf_getline(&sb, stdin, '\n') != EOF) {
                const char *s;
+               const char *argh;
Let's spell that variable name out, e.g. arg_hint or something.

I was looking at the surrounding code for some style guidance, but most local variables have short names like "s", "o", "onb", "osz", "sb".
There are some that are longer.  So I was quite unsure here.
At the same time the target structure that holds the option description calls this string "argh". Also, this is not really an "arg_hint" but the end of it. Argument name is actually between s and argh, if there is some.
Considering all that, "argh" seemed like an OK name.

I've renamed it to "end". It is used to remember possible end of the argument name in just one paragraph of code.
Comments above the paragraph clarifies what is been extracted.
Should there be another "parameter" in the option specification, the same variable could be used while parsing that one as well.

Let me know if you what that to be "arg_hint", or "arg_hint_end", or anything else.

diff --git a/t/t1502-rev-parse-parseopt.sh b/t/t1502-rev-parse-parseopt.sh
index 83b1300..bf0db05 100755
--- a/t/t1502-rev-parse-parseopt.sh
+++ b/t/t1502-rev-parse-parseopt.sh
@@ -18,6 +18,17 @@ An option group Header
      -C[...]               option C with an optional argument
      -d, --data[=...]      short and long option with an optional argument
+Argument hints
+    -b <arg>              short option required argument
+    --bar2 <arg>          long option required argument
+    -e, --fuz <with spaces>
+                          short and long option required argument
+    -s[<some>]            short option optional argument
+    --long[=<data>]       long option optional argument
+    -g, --fluf[=<path>]   short and long option optional argument
+    --longest <a very long argument hint>
+                          a very long argument hint
+
  Extras
      --extra1              line above used to cause a segfault but no longer 
does
@@ -39,6 +50,15 @@ b,baz a short and long option
  C?        option C with an optional argument
  d,data?   short and long option with an optional argument
+ Argument hints
+b=arg     short option required argument
+bar2=arg  long option required argument
+e,fuz=with_spaces  short and long option required argument
+s?some    short option optional argument
+long?data long option optional argument
+g,fluf?path     short and long option optional argument
+longest=a_very_long_argument_hint  a very long argument hint
+
Nice.

Thanks :)

P.S. Patch comes in the next message.
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