idf_tools: Add option to replace all GitHub tools download URLs with dl.espressif.com

Via new IDF_GITHUB_ASSETS environment variable.

tools/idf_tools.py

@@ -1052,6 +1052,11 @@ def action_export(args):
         raise SystemExit(1)
 
 
+def apply_url_mirrors(args, tool_download_obj):
+    apply_mirror_prefix_map(args, tool_download_obj)
+    apply_github_assets_option(tool_download_obj)
+
+
 def apply_mirror_prefix_map(args, tool_download_obj):
     """Rewrite URL for given tool_obj, given tool_version, and current platform,
        if --mirror-prefix-map flag or IDF_MIRROR_PREFIX_MAP environment variable is given.
@@ -1079,6 +1084,32 @@ def apply_mirror_prefix_map(args, tool_download_obj):
                 break
 
 
+def apply_github_assets_option(tool_download_obj):
+    """ Rewrite URL for given tool_obj if the download URL is an https://github.com/ URL and the variable
+    IDF_GITHUB_ASSETS is set. The github.com part of the URL will be replaced.
+    """
+    try:
+        github_assets = os.environ["IDF_GITHUB_ASSETS"].strip()
+    except KeyError:
+        return  # no IDF_GITHUB_ASSETS
+    if not github_assets:  # variable exists but is empty
+        return
+
+    # check no URL qualifier in the mirror URL
+    if '://' in github_assets:
+        fatal("IDF_GITHUB_ASSETS shouldn't include any URL qualifier, https:// is assumed")
+        raise SystemExit(1)
+
+    # Strip any trailing / from the mirror URL
+    github_assets = github_assets.rstrip('/')
+
+    old_url = tool_download_obj.url
+    new_url = re.sub(r'^https://github.com/', 'https://{}/'.format(github_assets), old_url)
+    if new_url != old_url:
+        info('Using GitHub assets mirror for URL: {} => {}'.format(old_url, new_url))
+        tool_download_obj.url = new_url
+
+
 def action_download(args):
     tools_info = load_tools_info()
     tools_spec = args.tools
@@ -1121,7 +1152,7 @@ def action_download(args):
         tool_spec = '{}@{}'.format(tool_name, tool_version)
 
         info('Downloading {}'.format(tool_spec))
-        apply_mirror_prefix_map(args, tool_obj.versions[tool_version].get_download_for_platform(platform))
+        apply_url_mirrors(args, tool_obj.versions[tool_version].get_download_for_platform(platform))
 
         tool_obj.download(tool_version)
 
@@ -1162,7 +1193,7 @@ def action_install(args):
             continue
 
         info('Installing {}'.format(tool_spec))
-        apply_mirror_prefix_map(args, tool_obj.versions[tool_version].get_download_for_platform(PYTHON_PLATFORM))
+        apply_url_mirrors(args, tool_obj.versions[tool_version].get_download_for_platform(PYTHON_PLATFORM))
 
         tool_obj.download(tool_version)
         tool_obj.install(tool_version)