From 5fe375a8f1d60b49835b52df48686caddaa297a4 Mon Sep 17 00:00:00 2001
From: Bryan Richter <bryan.richter@relexsolutions.com>
Date: Fri, 18 Sep 2020 18:36:17 +0300
Subject: [PATCH] nix-prefetch-url: Add --executable flag

pkgs.fetchurl supports an executable argument, which is especially nice
when downloading a large executable. This patch adds the same option to
nix-prefetch-url.

I have tested this to work on the simple case of prefetching a little
executable:

1. nix-prefetch-url --executable https://my/little/script
2. Paste the hash into a pkgs.fetchurl-based package, script-pkg.nix
3. Delete the output from the store to avoid any misidentified artifacts
4. Realise the package script-pkg.nix
5. Run the executable

I repeated the above while using --name, as well.

I suspect --executable would have no meaningful effect if combined with
--unpack, but I have not tried it.
---
 doc/manual/src/command-ref/nix-prefetch-url.md |  3 +++
 src/nix-prefetch-url/nix-prefetch-url.cc       | 11 +++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/doc/manual/src/command-ref/nix-prefetch-url.md b/doc/manual/src/command-ref/nix-prefetch-url.md
index 1cd1063cd..1307c7c37 100644
--- a/doc/manual/src/command-ref/nix-prefetch-url.md
+++ b/doc/manual/src/command-ref/nix-prefetch-url.md
@@ -51,6 +51,9 @@ Nix store is also printed.
     result to the Nix store. The resulting hash can be used with
     functions such as Nixpkgs’s `fetchzip` or `fetchFromGitHub`.
 
+  - `--executable`  
+    Set the executable bit on the downloaded file.
+
   - `--name` *name*  
     Override the name of the file in the Nix store. By default, this is
     `hash-basename`, where *basename* is the last component of *url*.
diff --git a/src/nix-prefetch-url/nix-prefetch-url.cc b/src/nix-prefetch-url/nix-prefetch-url.cc
index 1001f27af..377ae03a8 100644
--- a/src/nix-prefetch-url/nix-prefetch-url.cc
+++ b/src/nix-prefetch-url/nix-prefetch-url.cc
@@ -57,6 +57,7 @@ static int _main(int argc, char * * argv)
         bool fromExpr = false;
         string attrPath;
         bool unpack = false;
+        bool executable = false;
         string name;
 
         struct MyArgs : LegacyArgs, MixEvalArgs
@@ -81,6 +82,8 @@ static int _main(int argc, char * * argv)
             }
             else if (*arg == "--unpack")
                 unpack = true;
+            else if (*arg == "--executable")
+                executable = true;
             else if (*arg == "--name")
                 name = getArg(*arg, arg, end);
             else if (*arg != "" && arg->at(0) == '-')
@@ -175,7 +178,11 @@ static int _main(int argc, char * * argv)
 
             /* Download the file. */
             {
-                AutoCloseFD fd = open(tmpFile.c_str(), O_WRONLY | O_CREAT | O_EXCL, 0600);
+                auto mode = 0600;
+                if (executable)
+                    mode = 0700;
+
+                AutoCloseFD fd = open(tmpFile.c_str(), O_WRONLY | O_CREAT | O_EXCL, mode);
                 if (!fd) throw SysError("creating temporary file '%s'", tmpFile);
 
                 FdSink sink(fd.get());
@@ -201,7 +208,7 @@ static int _main(int argc, char * * argv)
                     tmpFile = unpacked;
             }
 
-            const auto method = unpack ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat;
+            const auto method = unpack || executable ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat;
 
             auto info = store->addToStoreSlow(name, tmpFile, method, ht, expectedHash);
             storePath = info.path;