[TEST REPORT][PATCH] perf config: Introduce perf_config_set class

[Taeung Song]

Tested-by: Taeung Song <treeze.taeung@xxxxxxxxx>
Test-Date: 2016-03-10
Version: perf version 4.5.rc2.g8c497f
Kernel: 4.5.0-rc4+
Distro: Ubuntu 15.10 wily

Test Environment:

    1. Perf PATH

        # whereis perf
        perf: /usr/local/bin/perf /usr/local/share/man/man1/perf.1.gz

    2. User config file

        # cat ~/.perfconfig
        [report]
                queue-size = 1
        [call-graph]
                threshold = 2.0
        [test]
                location = user
        [top]
                children = false

    3. System config file

        # cat /usr/local/etc/perfconfig
        [ui]
            show-headers = false
        [test]
            location = system
	[top]
	    children = true

Test Results:

 Case 0) BASIC: perf_config() function work normally
 
    # cat ~/.perfconfig
    [colors]
        top = blue, white

    # perf top
    (omitted output, there isn't any problem)

 Case 1) BASIC: List functionality without a specific file
                  (equal with user + system config,
                   but user config has order of priority)

    # cat ~/.perfconfig
    [report]
        queue-size = 1
    [call-graph]
        threshold = 2.0
    [test]
        location = user
    [top]
        children = false

    # perf config --list
    ui.show-headers=false
    call-graph.threshold=2.0
    report.queue-size=1
    top.children=false
    test.location=user

 Case 2) BASIC: List functionality with user config file

    # perf config --user --list
    call-graph.threshold=2.0
    report.queue-size=1
    top.children=false
    test.location=user
    
 Case 3) BASIC: List functionality with system config file

    # perf config --system --list
    ui.show-headers=false
    top.children=true
    test.location=system

 Case 4) EXCEP HANDLING: If using two config file at a time

    # perf config --user --system --list
    Error: only one config file at a time

     Usage: perf config [<file-option>] [options]

            --user            use user config file-
            --system          use system config file

 Case 5) EXCEP HANDLING: user config file : don't exist || permission denied || empty
                           (user wide ~/.perfconfig)

    # perf config --user --list
    Nothing configured, please check your /home/taeung/.perfconfig

 Case 6) EXCEP HANDLING: system config file : don't exist || permission denied || empty
                           (system wide /usr/local/etc/perfconfig depending on perf PATH)

    # perf config --system --list
    Nothing configured, please check your /usr/local/etc/perfconfig

Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/perf/builtin-config.c |  61 +++++++---
 tools/perf/util/cache.h     |   2 -
 tools/perf/util/config.c    | 268 +++++++++++++++++++++++++++++++++++++++++---
 tools/perf/util/config.h    | 138 +++++++++++++++++++++++
 4 files changed, 433 insertions(+), 36 deletions(-)
 create mode 100644 tools/perf/util/config.h