[lit] Fix internal diff's --strip-trailing-cr and use it

Using GNU diff, `--strip-trailing-cr` removes a `\r` appearing before
a `\n` at the end of a line.  Without this patch, lit's internal diff
only removes `\r` if it appears as the last character.  That seems
useless.  This patch fixes that.

This patch also adds `--strip-trailing-cr` to some tests that fail on
Windows bots when D68664 is applied.  Based on what I see in the bot
logs, I think the following is happening.  In each test there, lit
diff is comparing a file with `\r\n` line endings to a file with `\n`
line endings.  Without D68664, lit diff reads those files in text
mode, which in Windows causes `\r\n` to be replaced with `\n`.
However, with D68664, lit diff reads the files in binary mode instead
and thus reports that every line is different, just as GNU diff does
(at least under Ubuntu).  Adding `--strip-trailing-cr` to those tests
restores the previous behavior while permitting the behavior of lit
diff to be more like GNU diff.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D68839

llvm-svn: 375020

3 files changed, 16 insertions, 0 deletions

diff --git a/llvm/utils/lit/tests/Inputs/shtest-shell/diff-in.dos b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-in.dos
new file mode 100644
index 00000000000..7a0560654c5
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-in.dos
@@ -0,0 +1,3 @@
+In this file, the

+sequence "\r\n"

+terminates lines.

diff --git a/llvm/utils/lit/tests/Inputs/shtest-shell/diff-in.unix b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-in.unix
new file mode 100644
index 00000000000..58208a3ae76
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-in.unix
@@ -0,0 +1,3 @@
+In this file, the
+sequence "\n"
+terminates lines.
diff --git a/llvm/utils/lit/tests/Inputs/shtest-shell/diff-strip-trailing-cr.txt b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-strip-trailing-cr.txt
new file mode 100644
index 00000000000..6111a8fbf72
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-strip-trailing-cr.txt
@@ -0,0 +1,10 @@
+# Check behavior of --strip-trailing-cr.
+
+# RUN: diff -u diff-in.dos diff-in.unix && false || true
+# RUN: diff -u diff-in.unix diff-in.dos && false || true
+
+# RUN: diff -u --strip-trailing-cr diff-in.dos diff-in.unix && false || true
+# RUN: diff -u --strip-trailing-cr diff-in.unix diff-in.dos && false || true
+
+# Fail so lit will print output.
+# RUN: false