feat: add command for format the swag comment.

[HYY-yu]

Describe the PR
Hello, Please see a example:

// GetStructArrayByString example
// @Description get struct array by ID
// @ID get-struct-array-by-string
// @Accept  json
// @Produce  json
// @Param   some_id     path    string     true        "Some ID"
// @Param   offset     query    int     true        "Offset"
// @Param   limit      query    int     true        "Offset"
// @Param   pet_id  query  int false "pet' id"
// @Param   book_id query int false "book' id"
// @Param   app_id query int false "app' id"
// @Param   x_key query string false "secret key"
// @Success 200 {string} string	"ok"
// @Failure 400 {object} web.APIError "We need ID!!"
// @Failure 404 {object} web.APIError "Can not find ID"
// @Router /testapi/get-struct-array-by-string/{some_id} [get]

As you can see, If I have a lot of params, The format of comment will look very messy.

So, we can create a command like gofmt, It automatically formats the "swag" comments.
Like this:

$ swag fmt -h
NAME:
   swag fmt - format swag comments

USAGE:
   swag fmt [command options] [arguments...]

OPTIONS:
   --dir value, -d value          Directories you want to parse,comma separated and general-info file must be in the first one (default: "./")
   --exclude value                Exclude directories and files when searching, comma separated
   --generalInfo value, -g value  Go file path in which 'swagger general API Info' is written (default: "main.go")
   --help, -h                     show help (default: false)

// GetStructArrayByString example
// @Description  get struct array by ID
// @ID           get-struct-array-by-string
// @Accept       json
// @Produce      json
// @Param        some_id  path      string        true   "Some ID"
// @Param        offset   query     int           true   "Offset"
// @Param        limit    query     int           true   "Offset"
// @Param        pet_id   query     int           false  "pet' id"
// @Param        book_id  query     int           false  "book' id"
// @Param        app_id   query     int           false  "app' id"
// @Param        x_key    query     string        false  "secret key"
// @Success      200      {string}  string        "ok"
// @Failure      400      {object}  web.APIError  "We need ID!!"
// @Failure      404      {object}  web.APIError  "Can not find ID"
// @Router       /testapi/get-struct-array-by-string/{some_id} [get]

How it works

just like go fmt, It use text/tabwriter to format the comment. It scans the swag comments, especially '@param', '@success', '@response', etc, recognize their boundaries, call text/tabwriter to format them. See the source code for more details.

Relation issue

Additional context

[codecov]

Codecov Report

Merging #1056 (85b7606) into master (9b23c9e) will increase coverage by 0.96%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1056      +/-   ##
==========================================
+ Coverage   93.46%   94.42%   +0.96%     
==========================================
  Files           8        9       +1     
  Lines        2127     2261     +134     
==========================================
+ Hits         1988     2135     +147     
+ Misses         77       66      -11     
+ Partials       62       60       -2     

Impacted Files	Coverage Δ
formater.go	100.00% <100.00%> (ø)
parser.go	92.09% <0.00%> (-0.18%)	⬇️
field_parser.go	100.00% <0.00%> (ø)
operation.go	95.88% <0.00%> (+0.88%)	⬆️
packages.go	80.22% <0.00%> (+3.38%)	⬆️

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[ubogdan]

@HYY-yu This is pretty impressive PR, and I feel it will be a nice and valuable feature for our community. Would you mind fixing the coverage so we may merge and include this in the 1.7.5 version?

[HYY-yu]

It's very hard to improving coverage, I had to use the Monkey test.

[ubogdan]

LGTM

[ubogdan]

I know the main focus on PR is the code. In the end, we are adding these features to improve the development experience.
Would you mind documenting this feature into README.md?

[HYY-yu]

Sure, I'll add to README later.

[ubogdan]

LGTM

[ubogdan]

@HYY-yu Thanks for your contribution.