fix: temp dir to be the same as SerchDir to avoid invalid cross-device link (#1203)

[tanopanta]

Describe the PR

Fix temp file logic t avoid invalid cross-device link

Relation issue
#1203

Additional context

Cause

This error occurs when os.Rename between different partitions

https://groups.google.com/g/golang-dev/c/5w7Jmg_iCJQ

In other words, TMPDIR and PWD are different partitions.

When ioutil.TempFile(dir, pattern string) 's first parameter is empty string, TempFile are created on TMPDIR.

If dir is the empty string, TempFile uses the default directory for temporary files (see os.TempDir).
https://pkg.go.dev/io/ioutil#TempFile

Solution
Fix filepath.Split() to filepath.Dir() and Base().
filepath.Split may return an empty string.

package main

import (
	"fmt"
	"path/filepath"
)

func main() {
	paths := []string{
		"/home/swaggo/main.go",
		"main.go",
	}

	fmt.Println("filepath.Split")
	for _, p := range paths {
		dir, file := filepath.Split(p)
		fmt.Printf("input: %q\n\tdir: %q\n\tfile: %q\n", p, dir, file)
	}
	fmt.Println("filepath.Dir, Base")
	for _, p := range paths {
		dir := filepath.Dir(p)
		file := filepath.Base(p)
		fmt.Printf("input: %q\n\tdir: %q\n\tfile: %q\n", p, dir, file)
	}
}

filepath.Split
input: "/home/swaggo/main.go"
	dir: "/home/swaggo/"
	file: "main.go"
input: "main.go"
	dir: ""
	file: "main.go"
filepath.Dir, Base
input: "/home/swaggo/main.go"
	dir: "/home/swaggo"
	file: "main.go"
input: "main.go"
	dir: "."
	file: "main.go"

Check

> pwd
/add_disk/swag
> go install github.com/swaggo/swag/cmd/swag@latest
> swag fmt main.go
2022/06/25 01:12:20 fmt: rename /tmp/main.go3296877051 main.go: invalid cross-device link
> make install
....
> swag fmt main.go
> 

[codecov]

Codecov Report

Merging #1241 (f9f81af) into master (0e2ec6c) will not change coverage.
The diff coverage is 100.00%.

❗ Current head f9f81af differs from pull request most recent head 41ab438. Consider uploading reports for the commit 41ab438 to get more accurate results

@@           Coverage Diff           @@
##           master    #1241   +/-   ##
=======================================
  Coverage   94.83%   94.83%           
=======================================
  Files          14       14           
  Lines        2614     2614           
=======================================
  Hits         2479     2479           
  Misses         74       74           
  Partials       61       61           

Impacted Files	Coverage Δ
format/format.go	92.30% <100.00%> (ø)

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[tanopanta]

📝 This line is the same as formatter.go (L372) before modifying #1192
https://github.com/swaggo/swag/pull/1192/files

[ubogdan]

LGTM

[ubogdan]

@tanopanta Thanks for your contribution.