Clean up the bootstrap script a little.

This change makes the bootstrap script take two optional flag-based command
line arguments rather than using positional arguments.  The -i argument
replaces the old positional arguments (one of which was simply not needed), and
the -r flag now causes the script to regenerate the bootstrap Ninja file for
use when working on Blueprint itself.

Additionally this change allows all the configuration variables used in the
script to be overridden by environment variables.  This makes it possible to
create a very simple bootstrap script for a customized Blueprint-based build
system by invoking this script after setting up the proper environment
variables.

Change-Id: I60f890061ae237a68719e1e2d345d1a8e87c851c

blueprint/bootstrap/bootstrap.go

@@ -46,7 +46,7 @@ var (
 
 	bootstrap = blueprint.StaticRule("bootstrap",
 		blueprint.RuleParams{
-			Command:     "$Bootstrap $in $BootstrapManifest",
+			Command:     "$Bootstrap -i $in",
 			Description: "bootstrap $in",
 			Generator:   true,
 		})
@@ -64,7 +64,7 @@ var (
 			// This workaround can be avoided entirely by making a simple change
 			// to Ninja that would allow it to rebuild the manifest twice rather
 			// than just once.
-			Command:     "$Bootstrap $in && ninja",
+			Command:     "$Bootstrap -i $in && ninja",
 			Description: "re-bootstrap $in",
 			Generator:   true,
 		})

bootstrap.bash

@@ -1,29 +1,91 @@
 #!/bin/bash
 
+# This script serves two purposes.  First, it can bootstrap the standalone
+# Blueprint to generate the minibp binary.  To do this simply run the script
+# with no arguments from the desired build directory.
+#
+# It can also be invoked from another script to bootstrap a custom Blueprint-
+# based build system.  To do this, the invoking script must first set some or
+# all of the following environment variables, which are documented below where
+# their default values are set:
+#
+#   BOOTSTRAP
+#   SRCDIR
+#   BOOTSTRAP_MANIFEST
+#   GOROOT
+#   GOOS
+#   GOARCH
+#   GOCHAR
+#
+# The invoking script should then run this script, passing along all of its
+# command line arguments.
+
+set -e
+
+# BOOTSTRAP should be set to the path of the bootstrap script.  It can be
+# either an absolute path or one relative to the build directory (which of
+# these is used should probably match what's used for SRCDIR).
+[ -z "$BOOTSTRAP" ] && BOOTSTRAP="${BASH_SOURCE[0]}"
+
 # SRCDIR should be set to the path of the root source directory.  It can be
 # either an absolute path or a path relative to the build directory.  Whether
-# its an absolute or relative path determines whether the build directory can be
-# moved relative to or along with the source directory without re-running the
-# bootstrap script.
-SRCDIR=`dirname "${BASH_SOURCE[0]}"`
+# its an absolute or relative path determines whether the build directory can
+# be moved relative to or along with the source directory without re-running
+# the bootstrap script.
+[ -z "$SRCDIR" ] && SRCDIR=`dirname "${BOOTSTRAP}"`
 
-# BOOTSTRAP should be set to the path of this script.  It can be either an
-# absolute path or one relative to the build directory (which of these is used
-# should probably match what's used for SRCDIR).
-BOOTSTRAP="${BASH_SOURCE[0]}"
+# BOOTSTRAP_MANIFEST is the path to the bootstrap Ninja file that is part of
+# the source tree.  It is used to bootstrap a build output directory from when
+# the script is run manually by a user.
+[ -z "$BOOTSTRAP_MANIFEST" ] && BOOTSTRAP_MANIFEST="${SRCDIR}/build.ninja.in"
 
-# These variables should be set by auto-detecting or knowing a priori the Go
-# toolchain properties.
-GOROOT=`go env GOROOT`
-GOOS=`go env GOHOSTOS`
-GOARCH=`go env GOHOSTARCH`
-GOCHAR=`go env GOCHAR`
+# These variables should be set by auto-detecting or knowing a priori the host
+# Go toolchain properties.
+[ -z "$GOROOT" ] && GOROOT=`go env GOROOT`
+[ -z "$GOOS" ]   && GOOS=`go env GOHOSTOS`
+[ -z "$GOARCH" ] && GOARCH=`go env GOHOSTARCH`
+[ -z "$GOCHAR" ] && GOCHAR=`go env GOCHAR`
 
-case "$#" in
-    1) IN="$1";BOOTSTRAP_MANIFEST="$1";;
-	2) IN="$1";BOOTSTRAP_MANIFEST="$2";;
-    *) IN="${SRCDIR}/build.ninja.in";BOOTSTRAP_MANIFEST="$IN";;
-esac
+usage() {
+    echo "Usage of ${BOOTSTRAP}:"
+    echo "  -h: print a help message and exit"
+    echo "  -r: regenerate ${BOOTSTRAP_MANIFEST}"
+}
+
+# Parse the command line flags.
+IN="$BOOTSTRAP_MANIFEST"
+REGEN_BOOTSTRAP_MANIFEST=false
+while getopts ":hi:r" opt; do
+    case $opt in
+        h)
+            usage
+            exit 1
+            ;;
+        i) IN="$OPTARG";;
+        r) REGEN_BOOTSTRAP_MANIFEST=true;;
+        \?)
+            echo "Invalid option: -$OPTARG" >&2
+            usage
+            exit 1
+            ;;
+        :)
+            echo "Option -$OPTARG requires an argument." >&2
+            exit 1
+            ;;
+    esac
+done
+
+if [ $REGEN_BOOTSTRAP_MANIFEST = true ]; then
+    # This assumes that the script is being run from a build output directory
+    # that has been built in the past.
+    if [ -x .bootstrap/bin/minibp ]; then
+        echo "Regenerating $BOOTSTRAP_MANIFEST"
+        ./.bootstrap/bin/minibp -o $BOOTSTRAP_MANIFEST $SRCDIR/Blueprints
+    else
+        echo "Executable minibp not found at .bootstrap/bin/minibp" >&2
+        exit 1
+    fi
+fi
 
 sed -e "s|@@SrcDir@@|$SRCDIR|g"                        \
     -e "s|@@GoRoot@@|$GOROOT|g"                        \

build.ninja.in

@@ -50,7 +50,7 @@ rule g.bootstrap.cp
     description = cp ${out}
 
 rule g.bootstrap.bootstrap
-    command = ${g.bootstrap.Bootstrap} ${in} ${g.bootstrap.BootstrapManifest}
+    command = ${g.bootstrap.Bootstrap} -i ${in}
     description = bootstrap ${in}
     generator = true