[support, docs] A minimal implementation of the "realpath" CLI.

This frees us from needing a system prerequisite, and enables
platforms that don't even provide such a binary.

Author: tkoeppe

Diff for: .travis.yml

@@ -18,7 +18,6 @@ addons:
       - python-dev
       - python-numpy
       - python-pil
-      - realpath
 
 before_install:
   - curl https://bazel.build/bazel-release.pub.gpg | sudo apt-key add -

Diff for: BUILD

@@ -686,8 +686,9 @@ genrule(
           "  A=$$(dirname $$s); " +
           "  B=$${A/assets/}; " +
           "  mkdir -p $(@D)/baselab$${B}; " +
-          "  ln -s -L -t $(@D)/baselab$${B} $$(realpath $${s}); " +
+          "  ln -s -L -t $(@D)/baselab$${B} $$($(location //deepmind/support:realpath) $${s}); " +
           "done",
+    tools = ["//deepmind/support:realpath"],
     visibility = ["//visibility:public"],
 )
 
@@ -703,8 +704,9 @@ genrule(
     cmd = "for s in $(SRCS); do " +
           "  A=$$(dirname $$s); " +
           "  mkdir -p $(@D)/baselab/$${A}; " +
-          "  ln -s -L -t $(@D)/baselab/$${A} $$(realpath $${s}); " +
+          "  ln -s -L -t $(@D)/baselab/$${A} $$($(location //deepmind/support:realpath) $${s}); " +
           "done",
+    tools = ["//deepmind/support:realpath"],
     visibility = ["//visibility:public"],
 )
 
@@ -719,8 +721,9 @@ genrule(
     outs = ["baselab/maps" + f[len("assets/maps/built"):] for f in BUILT_MAPS],
     cmd = "for s in $(SRCS); do " +
           "  mkdir -p $(@D)/baselab/maps; " +
-          "  ln -s -L -t $(@D)/baselab/maps $$(realpath $${s}); " +
+          "  ln -s -L -t $(@D)/baselab/maps $$($(location //deepmind/support:realpath) $${s}); " +
           "done",
+    tools = ["//deepmind/support:realpath"],
     visibility = ["//visibility:public"],
 )
 

Diff for: RELEASE_NOTES.md

@@ -14,6 +14,8 @@
     state](https://github.com/ioquake/ioq3/tree/29db64070aa0bae49953bddbedbed5e317af48ba).
 5.  Lua 5.1 is now downloaded and built from source, and is thus no longer a
     required local dependency.
+6.  A minimal version of the "realpath" utility is now bundled with the code,
+    and thus "realpath" is no longer a required local dependency.
 
 ### Bug Fixes:
 

Diff for: deepmind/support/BUILD

@@ -23,3 +23,9 @@ cc_library(
     hdrs = ["test_srcdir.h"],
     defines = ["SUPPRESS_COMMANDLINE_FLAGS"],
 )
+
+cc_binary(
+    name = "realpath",
+    srcs = ["realpath.c"],
+    copts = ["-std=c99"],
+)

Diff for: deepmind/support/realpath.c

@@ -0,0 +1,46 @@
+// Copyright (C) 2018 Google Inc.
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this program; if not, write to the Free Software Foundation, Inc.,
+// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+////////////////////////////////////////////////////////////////////////////////
+//
+// A minimal driver for Posix realpath(). Not every Posix system supplies such
+// a driver, and even on those that do it might require a separate installation
+// step. This implements the equivalent of "realpath -e" on Linux.
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, char* argv[]) {
+  int num_errors = 0;
+  errno = 0;
+
+  for (int i = 1; i < argc; ++i) {
+    char* p = realpath(argv[i], NULL);
+    if (p == NULL) {
+      fprintf(stderr, "Error resolving path '%s', error was: '%s'\n",
+              argv[i], strerror(errno));
+      errno = 0;
+      ++num_errors;
+    } else {
+      fprintf(stdout, "%s\n", p);
+      free(p);
+    }
+  }
+
+  return num_errors == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+}

Diff for: docs/users/build.md

@@ -31,7 +31,7 @@ are documented in a [separate section](#python-dependencies) below.
 
      ```shell
      $ sudo apt-get install libffi-dev gettext freeglut3-dev libsdl2-dev \
-           libosmesa6-dev python-dev python-numpy python-pil realpath
+           libosmesa6-dev python-dev python-numpy python-pil
      ```
 
    * On Red Hat Enterprise Linux Server: