Program to convert output from `git diff` for a folder to a JSON file based on the line change.

diff-to-json.go

// Copyright 2022 Amit Biswas. All rights reserved.
// Use of this source code is governed by the
// GNU GENERAL PUBLIC LICENSE v3.0

// Program to convert output from `git diff` for a folder to a
// JSON file based on the line change. If the diff for a file is
// nothing other than line number changes, it excludes the file
// from JSON listing.

// For example, if the diff for file A is like below, where the
// content is same but line number is changed, this file won't be
// listed in the JSON.

// diff --git a/A.txt b/A.txt
// index 5e486ea..916d710 100644
// --- a/A.txt
// +++ b/A.txt
// @@ -1,5 +1,5 @@
//  Hello World!
// -I am excited about programming.
// -
//  Thanks!
// +
// +I am excited about programming.

package main

import (
	"encoding/json"
	"os"
	"os/exec"
	"regexp"
	"strings"
)

// generate git diff for loc folder
func generateDiff(loc string) ([]byte, error) {
	args := []string{"cd", loc, "&&", "git", "diff"}
	cmd := exec.Command("/bin/bash", "-c", strings.Join(args, " "))
	return cmd.CombinedOutput()
}

// writes selected diffs to a json file in loc folder
func writeToJSON(loc string, selectedDiffs map[string]map[string][]string) {
	// create or overwrite previous file
	file, err := os.OpenFile(loc+"/result.json", os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0755)
	if err != nil {
		panic(err)
	}

	// close file when writeToJSON ends
	defer file.Close()

	// convert map to JSON
	jsonDiff, err := json.Marshal(selectedDiffs)
	if err != nil {
		panic(err)
	}

	// write to file
	if _, err := file.WriteString(string(jsonDiff)); err != nil {
		panic(err)
	}
}

func main() {
	// determine folder location from cmd arguments
	loc := "."
	if len(os.Args) > 1 && os.Args[1] != "" {
		loc = os.Args[1]
	}

	// generate diff as []byte
	diff, err := generateDiff(loc)
	if err != nil {
		panic("Couldn't generate diff. Check the folder path.")
	}

	// create slice of lines from diff string
	lines := strings.Split(string(diff), "\n")
	if len(lines) == 0 {
		panic("No diff found!")
	}

	allDiffs := make(map[string]map[string][]string)
	selectedDiffs := make(map[string]map[string][]string)

	currentfilepath := ""

	for _, line := range lines {
		// select only if changed line or filepath line
		// -    negate: true
		// +    negate: false
		// --- a/config/drupal/default/addtoany.settings.yml
		// +++ a/config/drupal/default/addtoany.settings.yml
		matched, err := regexp.MatchString("^[+-]([+-][+-])?[a-zA-Z _].*", line)
		if err != nil {
			panic(err)
		}

		if matched {
			// select only filepath line
			// --- a/config/drupal/default/addtoany.settings.yml
			// +++ a/config/drupal/default/addtoany.settings.yml
			if strings.HasPrefix(line, "+++") || strings.HasPrefix(line, "---") {

				// extract filepath from full path
				// config/drupal/default/addtoany.settings.yml
				fullpath := regexp.MustCompile(` [ab]/`).Split(line, -1)
				filepath := fullpath[len(fullpath)-1]

				// init entry against the filepath
				if _, ok := allDiffs[filepath]; !ok {
					allDiffs[filepath] = make(map[string][]string)
					currentfilepath = filepath
				}
			} else {
				// if changed line, add according to add/delete
				if string(line[0]) == "+" {
					allDiffs[currentfilepath]["+"] = append(allDiffs[currentfilepath]["+"], line[1:])
				}
				if string(line[0]) == "-" {
					allDiffs[currentfilepath]["-"] = append(allDiffs[currentfilepath]["-"], line[1:])
				}
			}
		}
	}

	// after building map from diff, filter the map to get
	// diff which are not positional changes. Meaning, if a
	// statement was on line 10, and now on line 15, the diff
	// for the file will be excluded.
	for key, val := range allDiffs {
		added := val["+"]
		deleted := val["-"]

		for _, va := range added {
			found := false
			for _, vd := range deleted {
				if va == vd {
					found = true
					break
				}
			}
			if found == false {
				if _, ok := selectedDiffs[key]; !ok {
					selectedDiffs[key] = map[string][]string{
						"+": val["+"],
						"-": val["-"],
					}
				}
			}
		}
	}

	// write to JSON
	writeToJSON(loc, selectedDiffs)
}