perf subcmd: Bugfix exactly compare long name of options to avoid repeat output.

In parse_options_usage(), check whether short option is used and there is a option that has same name with a specific option string (optstr) or not
before printing usage of options by print_option_help().

But using prefixcmp() has a problem when comparing long name of options with a specific option string(optstr). If two options has similar long name that is same prefix of each name, repeat printing usage of options i.e.

'list' and 'list-all' among perf-config options has a option flag 'PARSE_OPT_EXCLUSIVE'
but there was a problem when handling the error as below.

    # perf config --list-all --list
    Error: option `list' cannot be used with list-all
    Usage: perf config [<file-option>] [options]

        -l, --list            show current config variables
        -a, --list-all        show current and all possible config variables with default values
        -a, --list-all        show current and all possible config variables with default values

But if using short name of them,
this problem(repeat output) didn't occur i.e. That is why two names are compared by prefixcmp().

    # perf config -a -l
    Error: switch `l' cannot be used with switch `a'
    Usage: perf config [<file-option>] [options]

-l, --list show current config variables
-a, --list-all show current and all possible config variables with default values

And perf-probe or perf-record hasn't this problem.
Because them hasn't two simliar long name of each option. But I found this problem developing perf-config to add
a option 'list-all'. Current perf-config hasn't 'list-all' option yet but I think this problem might occur by other sub-command in future. So I fix it changing prefixcmp() into strcmp() in order to exactly compare long name of options with a spefic option string. After applied, other problems didn't occur as below.

Before:

    # perf probe --list --funcs
    Error: option `funcs' cannot be used with list
    Usage: perf probe [<options>] 'PROBEDEF' ['PROBEDEF' ...]
       or: perf probe [<options>] --add 'PROBEDEF' [--add 'PROBEDEF' ...]
       or: perf probe [<options>] --del '[GROUP:]EVENT' ...
       or: perf probe --list [GROUP:]EVENT ...
       or: perf probe [<options>] --line 'LINEDESC'
       or: perf probe [<options>] --vars 'PROBEPOINT'
       or: perf probe [<options>] --funcs

-F, --funcs <[FILTER]>
Show potential probe-able functions.
-l, --list <[GROUP:]EVENT>
list up probe events

# perf config --list-all --list
Error: option `list' cannot be used with list-all
Usage: perf config [<file-option>] [options]

-l, --list show current config variables
-a, --list-all show current and all possible config variables with default values
-a, --list-all show current and all possible config variables with default values

After:

    # perf probe --list --funcs
    Error: option `funcs' cannot be used with list
    Usage: perf probe [<options>] 'PROBEDEF' ['PROBEDEF' ...]
       or: perf probe [<options>] --add 'PROBEDEF' [--add 'PROBEDEF' ...]
       or: perf probe [<options>] --del '[GROUP:]EVENT' ...
       or: perf probe --list [GROUP:]EVENT ...
       or: perf probe [<options>] --line 'LINEDESC'
       or: perf probe [<options>] --vars 'PROBEPOINT'
       or: perf probe [<options>] --funcs

-F, --funcs <[FILTER]>
Show potential probe-able functions.
-l, --list <[GROUP:]EVENT>
list up probe events

# perf config --list-all --list
Error: option `list' cannot be used with list-all
Usage: perf config [<file-option>] [options]

-l, --list show current config variables
-a, --list-all show current and all possible config variables with default values

---
 tools/lib/subcmd/parse-options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 981bb44..b217b90 100644
@@ -911,7 +911,7 @@ opt:
 		if (opts->long_name == NULL)
 			continue;
 
-		if (!prefixcmp(opts->long_name, optstr))
+		if (!strcmp(opts->long_name, optstr))
 			print_option_help(opts, 0);
 		if (!prefixcmp("no-", optstr) &&
 		    !prefixcmp(opts->long_name, optstr + 3))

2.5.0