mingw-w64-git-lfs: make the logic a bit more readable

While the previous version works, and is concise, it is quite obviously
much harder to read, to understand and to modify.

Let's avoid those complex regular expressions and parse/transform the
Git LFS release notes as well as the `PKGBUILD` file line by line.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

update-scripts/mingw-w64-git-lfs

@@ -17,18 +17,29 @@
         `/repos/git-lfs/git-lfs/releases/tags/v${version}`
     )
 
-    const getSHA256 = (architecture) =>
-        releaseNotes.match(new RegExp(`git-lfs-windows-${architecture}-\\S+\\.zip.*\r?\n([0-9a-f]{64})\r?\n`))[1]
-    
-    const fs = require('fs')
-    let PKGBUILD = fs.readFileSync('PKGBUILD').toString('utf-8')
-    for (const architecture of [
-        { lfs: '386', msys2: 'i686' },
-        { lfs: 'amd64', msys2: 'x86_64' },
-        { lfs: 'arm64', msys2: 'aarch64' }
-    ]) {
-        const match = PKGBUILD.match(new RegExp(`^([^]*\\r?\\n${architecture.msys2}\\)[^]*? sha256sum=)[0-9a-f]{64}([^]*)$`))
-        PKGBUILD = `${match[1]}${getSHA256(architecture.lfs)}${match[2]}`
+    const sha256sums = {}
+    let architecture
+    let match
+    for (const line of releaseNotes.split(/\r?\n/)) {
+        if (line.match(/^[0-9a-f]{64}$/)) sha256sums[architecture] = line
+        else if ((match = line.match(/git-lfs-windows-(\S+)-v\S+\.zip/))) architecture = match[1]
+        else architecture = undefined
+    }
+
+    const msys2lfsArchitecture = {
+        'i686': '386',
+        'x86_64': 'amd64',
+        'aarch64': 'arm64',
     }
-    fs.writeFileSync('PKGBUILD', PKGBUILD)
+
+    const fs = require('fs')
+    const lines = fs.readFileSync('PKGBUILD').toString('utf-8').split(/\r?\n/)
+    lines.forEach((line, i) => {
+        if ((match = line.match(/^(\S+)\)$/))) {
+            architecture = msys2lfsArchitecture[match[1]]
+        } else if ((match = line.match(/^(\s*sha256sum=)[0-9a-f]{64}$/))) {
+            lines[i] = `${match[1]}${sha256sums[architecture]}`
+        }
+    })
+    fs.writeFileSync('PKGBUILD', lines.join('\n'))
 })().catch(console.log)