diff --git a/blueprint/bootstrap/bootstrap.go b/blueprint/bootstrap/bootstrap.go
index 5f5ecff..b18b866 100644
--- a/blueprint/bootstrap/bootstrap.go
+++ b/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,
 		})
diff --git a/bootstrap.bash b/bootstrap.bash
index f9ad8ad..799bd20 100755
--- a/bootstrap.bash
+++ b/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"                        \
diff --git a/build.ninja.in b/build.ninja.in
index ecabb1c..07d7a0e 100644
--- a/build.ninja.in
+++ b/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