generate-cmdlist: parse common group commands

generate-cmdlist: parse common group commands

Parse the group block to create the array of group descriptions:

static char *common_cmd_groups[] = {
    N_("starting a working area"),
    N_("working on the current change"),
    N_("working with others"),
    N_("examining the history and state"),
    N_("growing, marking and tweaking your history"),
};

then map each element of common_cmds[] to a group via its index:

static struct cmdname_help common_cmds[] = {
    {"add", N_("Add file contents to the index"), 1},
    {"branch", N_("List, create, or delete branches"), 4},
    {"checkout", N_("Checkout a branch or paths to the ..."), 4},
    {"clone", N_("Clone a repository into a new directory"), 0},
    {"commit", N_("Record changes to the repository"), 4},
    ...
};

so that 'git help' can print those commands grouped by theme.

Only commands tagged with an attribute from the group block are emitted to
common_cmds[].

[commit message by Sébastien Guimmara <sebastien.guimmara@gmail.com>]

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Sébastien Guimmara <sebastien.guimmara@gmail.com>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>