History update: add Readme, make build green when there is not change (#5660)

Co-authored-by: Catenocrypt <catenocrypt@users.noreply.github.com>

history/README.md

@@ -0,0 +1,49 @@
+# History -- Change management
+
+Change information is made available explicitly, so clients can update only changed assets, without accessing version information from git.
+
+Change information can be found in the folder `history`.
+
+There is the `history/LATEST.json` file, which always contains the current version info:
+
+- `versionNum`: a simple numerical version designator (e.g. 42).
+- commit: the git commit SHA of the head of the master branch, info only.
+- date: the date time of the last commit, info only.
+
+The folder `history/versions` contains 1 file per version, named `<version>.json`, e.g. `42.json`.
+This file contains the list of changed files between the two versions, plus some meta info.
+
+If there are many files changed, the files are not listed, but `"fullChange": true` is set.
+
+An example of a change file is:
+
+```json
+{
+    "versionEnd": {
+        "versionNum": 2,
+        "commit": "159cec70437445948d3081a0b1564b436bccb646",
+        "date": "2021-02-22T15:26:24.985Z"
+    },
+    "versionStart": {
+        "versionNum": 1,
+        "commit": "f5117527c2e1dd89d51b72c3634d94edb5a04780",
+        "date": "2021-02-22T14:56:47.938Z"
+    },
+    "fullChange": false,
+    "changeCount": 12,
+    "changes": [
+        "blockchains/ethereum/allowlist.json",
+        "blockchains/ethereum/assets/0x67c597624B17b16fb77959217360B7cD18284253/info.json",
+        "blockchains/ethereum/assets/0x67c597624B17b16fb77959217360B7cD18284253/logo.png",
+        "blockchains/ethereum/assets/0x798D1bE841a82a273720CE31c822C61a67a601C3/info.json",
+        "blockchains/ethereum/assets/0x798D1bE841a82a273720CE31c822C61a67a601C3/logo.png",
+        "history/LATEST.json",
+        "history/versions/PLACEHOLDER",
+        "package.json",
+        "script/config.ts",
+        "script/entrypoint/history.ts",
+        "script/generic/history.ts",
+        "script/generic/update-all.ts"
+    ]
+}
+```

script/generic/history.ts

@@ -76,12 +76,15 @@ async function getChangedFiles(commitStart: string, commitEnd: string): Promise<
     if (!bulk) {
         return [];
     }
-    const list: string[] = bulk.split("\n").filter(l => {
+    const list: string[] = bulk.split("\n").filter(l => l);
-        if (!l) return false;
+    return list;
+}
+
+function filterChangedFiles(files: string[]): string[] {
+    return files.filter(l => {
         if (l.startsWith(IgnoreHistoryPrefix)) return false;
         return true;
     });
-    return list;
 }
 
 function changeListToJson(versionStart: VersionInfo, versionEnd: VersionInfo, changes: string[]): unknown {
@@ -145,15 +148,17 @@ export async function processChanges(): Promise<number> {
     };
     console.log(`New version:  ${JSON.stringify(newVer, null, 4)}`);
 
-    const files: string[] = await getChangedFiles(ver.commit, currCommit);
+    const filesRaw: string[] = await getChangedFiles(ver.commit, currCommit);
-    console.log(`${files.length} changed files found`);
+    console.log(`${filesRaw.length} changed files found`);
-    if (!files || files.length == 0) {
+    if (!filesRaw || filesRaw.length == 0) {
-        console.log(`Error: Could not obtain list of changed files, or no changed files between commits ${ver.commit} and ${currCommit}`);
+        console.log(`Error: Could not obtain list of changed files between commits ${ver.commit} and ${currCommit}`);
         return 4;
     }
-    if (files.length == 0) {
+    const files: string[] = filterChangedFiles(filesRaw);
-        console.log(`Warning: no changed files bwteewn commits ${ver.commit} ${currCommit}`);
+    console.log(`${files.length} changed files found (excluding history files)`);
-        return 5;
+    if (!files || files.length == 0) {
+        console.log(`Warning: No changed files (excluding history files) between commits ${ver.commit} and ${currCommit}`);
+        return 0;
     }
 
     const changeList: unknown = changeListToJson(ver, newVer, files);