thirdparty.zstd: add a runnable update.vsh script

thirdparty/zstd/fix.md

@@ -1,9 +1,7 @@
-1. Get `zstd` from https://github.com/facebook/zstd/releases
+The changes here are produced by modifying `thirdparty/zstd/zstd_v.patch`,
-2. Download and extract `zstd`, and goto `zstd-1.5.7/build/single_file_libs/`, run `create_single_file_library.sh`
+and then running `v thirdparty/zstd/update.vsh` .
-3. Copy generated `zstd.c` to v's `thirdparty/zstd/zstd-1.5.7.c`
-4. In `thirdparty/zstd/`, apply patch by `patch -p0 -i zstd_v.patch -o zstd.c`
-5. Remove `zstd-1.5.7.c`
 
-You can generate a new patch by `diff -u zstd-1.5.7.c zstd_modified.c > zstd_custom.patch`
+You can generate a new patch by:
+`diff -u zstd-1.5.7/build/single_file_libs/zstd.c thirdparty/zstd/zstd.c > zstd_custom.patch`
 
 BTW, patch is between `/* >> v_patch start */` and `/* << v_patch end */` mostly.

thirdparty/zstd/update.vsh

@@ -0,0 +1,22 @@
+// Use this script to update thirdparty/zstd to a future version of mbedtls.
+import os
+
+fn do(cmd string) {
+	println(cmd)
+	res := os.system(cmd)
+	if res != 0 {
+		panic('failed at: `${cmd}`')
+	}
+}
+
+os.chdir(os.dir(@VEXE))!
+
+version := '1.5.7'
+do('rm -rf zstd-${version}*')
+do('wget https://github.com/facebook/zstd/releases/download/v${version}/zstd-${version}.tar.gz')
+do('tar -xf zstd-${version}.tar.gz')
+do('pushd .; cd zstd-${version}/build/single_file_libs/; ./create_single_file_library.sh; popd')
+do('cp zstd-${version}/build/single_file_libs/zstd.c thirdparty/zstd/zstd.c')
+do('pushd .; cd thirdparty/zstd/; patch --verbose --unified -p0 --input zstd_v.patch; popd')
+do('rm -rf zstd-${version}*')
+println('DONE')

thirdparty/zstd/zstd_v.patch

@@ -1,4 +1,4 @@
---- zstd-1.5.7.c	2025-05-30 16:39:46.374765970 +0800
+--- zstd.c	2025-05-30 16:39:46.374765970 +0800
 +++ zstd.c	2025-05-30 21:02:30.710831777 +0800
 @@ -50,6 +50,27 @@
  /* TODO: Can't amalgamate ASM function */