Auto merge of rust-lang#761 - tmfink:script-fix, r=fitzgen

Refactor test script

Check for correct arguments, quote variables, ensure exactly one test
file matches the pattern, and print usage information.

Here are some examples:

~~~
$ ./tests/test-one.sh
Usage: ./tests/test-one.sh <fuzzy-name>
~~~

~~~
$ ./tests/test-one.sh zzz
ERROR: no files found with pattern "zzz"
~~~

~~~
$ ./tests/test-one.sh union
ERROR: Expected exactly 1 result, got 15:
./tests/headers/struct_with_anon_unnamed_union.h
./tests/headers/union_dtor.hpp
./tests/headers/union_with_anon_union.h
./tests/headers/union_with_big_member.h
./tests/headers/anon_union.hpp
./tests/headers/union_fields.hpp
./tests/headers/union_with_anon_struct_bitfield.h
./tests/headers/struct_with_anon_union.h
./tests/headers/union-in-ns.hpp
./tests/headers/union_with_anon_unnamed_union.h
./tests/headers/union_with_anon_struct.h
./tests/headers/union_with_nesting.h
./tests/headers/union_template.hpp
./tests/headers/anon_struct_in_union.h
./tests/headers/union_with_anon_unnamed_struct.h
~~~

~~~
$ ./tests/test-one.sh keywords
...
~~~

Author: bors-servo

.gitignore

@@ -4,3 +4,7 @@ target/
 bindgen-integration/Cargo.lock
 tests/expectations/Cargo.lock
 #*#
+
+# Test script output
+ir.dot
+ir.png

tests/test-one.sh

@@ -10,13 +10,34 @@
 
 set -eu
 
-cd $(dirname $0)
+if [ $# -ne 1 ]; then
+    echo "Usage: $0 <fuzzy-name>"
+    exit 1
+fi
+
+cd "$(dirname "$0")"
 cd ..
 
 export RUST_BACKTRACE=1
 
-# Grab the first match
-TEST=$(find ./tests/headers -type f -iname "*$1*" | head -n 1)
+unique_fuzzy_file() {
+    local pattern="$1"
+    local results="$(find ./tests/headers -type f -iname "*$pattern*")"
+    local num_results=$(echo "$results" | wc -l)
+
+    if [[ -z "$results" ]]; then
+        >&2 echo "ERROR: no files found with pattern \"$pattern\""
+        exit 1
+    elif [[ "$num_results" -ne 1 ]]; then
+        >&2 echo "ERROR: Expected exactly 1 result, got $num_results:"
+        >&2 echo "$results"
+        exit 1
+    fi
+
+    echo "$results"
+}
+
+TEST="$(unique_fuzzy_file "$1")"
 
 BINDINGS=$(mktemp -t bindings.rs.XXXXXX)
 TEST_BINDINGS_BINARY=$(mktemp -t bindings.XXXXXX)