feat: git ignore to glob converter

lib/path-utils.js

@@ -1,4 +1,9 @@
 import path from "path"
+import { promises } from "fs"
+const { readFile } = promises
+
+import { unique } from "./utils"
+
 /** Converts given path to Posix (replacing \\ with /)
  * @param {string} givenPath   Path to convert
  * @returns {string}          Converted filepath
@@ -15,6 +20,70 @@ export function posixifyPathNormalized(givenPath) {
   return posixifyPath(givenPath).replace(/[/\\]$/, "")
 }
 
+/**
+ * @param {string} gitIgnoreEntry one git ignore entry (it expects a valid non-comment gitignore entry with no surrounding whitespace)
+ * @param {string | undefined} gitIgnoreDirectory the directory of gitignore
+ * @returns {string | [string, string]} the equivilant glob
+ */
+function globifyGitIgnoreEntry(gitIgnoreEntry, gitIgnoreDirectory) {
+  // output glob entry
+  let entry = gitIgnoreEntry
+
+  // Process the entry beginning
+
+  // '!' in .gitignore means to force include the pattern
+  // remove "!" to allow the processing of the pattern and swap ! in the end of the loop
+  let forceInclude = false
+  if (entry[0] === "!") {
+    entry = entry.substring(1)
+    forceInclude = true
+  }
+
+  // If there is a separator at the beginning or middle (or both) of the pattern,
+  // then the pattern is relative to the directory level of the particular .gitignore file itself
+
+  if (entry[0] === "/") {
+    // Patterns starting with '/' in gitignore are considred relative to the project directory while glob
+    // treats them as relative to the OS root directory.
+    // So we trim the slash to make it relative to project folder from glob perspective.
+    entry = entry.substring(1)
+  } else {
+    // Process the middle
+
+    if (entry.indexOf("/") === -1) {
+      if (!entry.startsWith("**/")) {
+        // Patterns that don't have `/` are '**/' from glob perspective (can match at any level)
+        entry = `**/${entry}`
+      }
+    }
+  }
+
+  // prepend the absolute root directory
+  if (gitIgnoreDirectory) {
+    entry = `${posixifyPath(gitIgnoreDirectory)}/${entry}`
+  }
+
+  // swap !
+  entry = forceInclude ? entry : `!${entry}`
+
+  // Process the entry ending
+
+  if (entry.endsWith("/")) {
+    // If there is a separator at the end of the pattern then it only matches directories
+    // in glob this is equal to `directry/**`
+    entry = `${entry}**`
+  } else {
+    // unless already ends with /**
+    if (!entry.endsWith("/**")) {
+      // the pattern can match both files and directories
+      // so we should include both `entry` and `entry/**`
+      return [entry, `${entry}/**`]
+    }
+  }
+
+  return entry
+}
+
 function isWhitespace(str) {
   return /^\s*$/.test(str)
 }