Index: lib/Format/UnwrappedLineFormatter.h
===================================================================
--- lib/Format/UnwrappedLineFormatter.h
+++ lib/Format/UnwrappedLineFormatter.h
@@ -51,7 +51,8 @@
   void formatFirstToken(const AnnotatedLine &Line,
                         const AnnotatedLine *PreviousLine,
                         const SmallVectorImpl<AnnotatedLine *> &Lines,
-                        unsigned Indent, unsigned NewlineIndent);
+                        unsigned Indent, unsigned NewlineIndent,
+                        bool OnlyUntilLastNewline = false);
 
   /// Returns the column limit for a line, taking into account whether we
   /// need an escaped newline due to a continued preprocessor directive.
Index: lib/Format/UnwrappedLineFormatter.cpp
===================================================================
--- lib/Format/UnwrappedLineFormatter.cpp
+++ lib/Format/UnwrappedLineFormatter.cpp
@@ -1111,9 +1111,9 @@
                               TheLine.LeadingEmptyLinesAffected);
         // Format the first token.
         if (ReformatLeadingWhitespace)
-          formatFirstToken(TheLine, PreviousLine, Lines,
-                           TheLine.First->OriginalColumn,
-                           TheLine.First->OriginalColumn);
+          formatFirstToken(
+              TheLine, PreviousLine, Lines, TheLine.First->OriginalColumn,
+              TheLine.First->OriginalColumn, /*OnlyUntilLastNewline=*/true);
         else
           Whitespaces->addUntouchableToken(*TheLine.First,
                                            TheLine.InPPDirective);
@@ -1136,7 +1136,7 @@
 void UnwrappedLineFormatter::formatFirstToken(
     const AnnotatedLine &Line, const AnnotatedLine *PreviousLine,
     const SmallVectorImpl<AnnotatedLine *> &Lines, unsigned Indent,
-    unsigned NewlineIndent) {
+    unsigned NewlineIndent, bool OnlyUntilLastNewline) {
   FormatToken &RootToken = *Line.First;
   if (RootToken.is(tok::eof)) {
     unsigned Newlines = std::min(RootToken.NewlinesBefore, 1u);
@@ -1188,7 +1188,8 @@
 
   Whitespaces->replaceWhitespace(RootToken, Newlines, Indent, Indent,
                                  Line.InPPDirective &&
-                                     !RootToken.HasUnescapedNewline);
+                                     !RootToken.HasUnescapedNewline,
+                                 OnlyUntilLastNewline);
 }
 
 unsigned
Index: lib/Format/WhitespaceManager.h
===================================================================
--- lib/Format/WhitespaceManager.h
+++ lib/Format/WhitespaceManager.h
@@ -49,7 +49,8 @@
   /// into tabs and spaces for some format styles.
   void replaceWhitespace(FormatToken &Tok, unsigned Newlines, unsigned Spaces,
                          unsigned StartOfTokenColumn,
-                         bool InPPDirective = false);
+                         bool InPPDirective = false,
+                         bool OnlyUntilLastNewline = false);
 
   /// Adds information about an unchangeable token's whitespace.
   ///
Index: lib/Format/WhitespaceManager.cpp
===================================================================
--- lib/Format/WhitespaceManager.cpp
+++ lib/Format/WhitespaceManager.cpp
@@ -46,13 +46,23 @@
 void WhitespaceManager::replaceWhitespace(FormatToken &Tok, unsigned Newlines,
                                           unsigned Spaces,
                                           unsigned StartOfTokenColumn,
-                                          bool InPPDirective) {
+                                          bool InPPDirective,
+                                          bool OnlyUntilLastNewline) {
   if (Tok.Finalized)
     return;
   Tok.Decision = (Newlines > 0) ? FD_Break : FD_Continue;
-  Changes.push_back(Change(Tok, /*CreateReplacement=*/true, Tok.WhitespaceRange,
-                           Spaces, StartOfTokenColumn, Newlines, "", "",
-                           InPPDirective && !Tok.IsFirst,
+  SourceRange OriginalWhitespaceRange = Tok.WhitespaceRange;
+
+  if (OnlyUntilLastNewline) {
+    OriginalWhitespaceRange.setEnd(
+        OriginalWhitespaceRange.getBegin().getLocWithOffset(
+            Tok.LastNewlineOffset));
+    Spaces = 0;
+    StartOfTokenColumn = 0;
+  }
+  Changes.push_back(Change(Tok, /*CreateReplacement=*/true,
+                           OriginalWhitespaceRange, Spaces, StartOfTokenColumn,
+                           Newlines, "", "", InPPDirective && !Tok.IsFirst,
                            /*IsInsideToken=*/false));
 }
 
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -36,12 +36,12 @@
     SC_DoNotCheck
   };
 
-  std::string format(llvm::StringRef Code,
-                     const FormatStyle &Style = getLLVMStyle(),
-                     StatusCheck CheckComplete = SC_ExpectComplete) {
+  std::string formatRange(llvm::StringRef Code, tooling::Range Range,
+                          const FormatStyle &Style = getLLVMStyle(),
+                          StatusCheck CheckComplete = SC_ExpectComplete) {
     LLVM_DEBUG(llvm::errs() << "---\n");
     LLVM_DEBUG(llvm::errs() << Code << "\n\n");
-    std::vector<tooling::Range> Ranges(1, tooling::Range(0, Code.size()));
+    std::vector<tooling::Range> Ranges(1, std::move(Range));
     FormattingAttemptStatus Status;
     tooling::Replacements Replaces =
         reformat(Style, Code, Ranges, "<stdin>", &Status);
@@ -57,6 +57,13 @@
     return *Result;
   }
 
+  std::string format(llvm::StringRef Code,
+                     const FormatStyle &Style = getLLVMStyle(),
+                     StatusCheck CheckComplete = SC_ExpectComplete) {
+    return formatRange(Code, tooling::Range(0, Code.size()), Style,
+                       CheckComplete);
+  }
+
   FormatStyle getStyleWithColumns(FormatStyle Style, unsigned ColumnLimit) {
     Style.ColumnLimit = ColumnLimit;
     return Style;
@@ -110,6 +117,14 @@
     format(Code, Style, SC_DoNotCheck);
   }
 
+  void verifyWithPrefixAndSuffix(llvm::StringRef Expected, llvm::StringRef Code,
+                                 llvm::StringRef prefix, llvm::StringRef suffix,
+                                 const FormatStyle &Style = getLLVMStyle()) {
+    EXPECT_EQ(llvm::Twine(prefix + Expected + suffix).str(),
+              formatRange(llvm::Twine(prefix + Code + suffix).str(),
+                          tooling::Range(prefix.size(), Code.size()), Style));
+  }
+
   int ReplacementCount;
 };
 
@@ -9156,6 +9171,18 @@
                Tab);
 }
 
+TEST_F(FormatTest, FormattingIndentationDoesNotAffectOtherLines) {
+  FormatStyle Tab = getLLVMStyleWithColumns(42);
+  Tab.TabWidth = 4;
+  Tab.UseTab = FormatStyle::UT_Always;
+  verifyWithPrefixAndSuffix("\tfoobar();", "    foobar();",
+                            "int f() {\n    int a;\n", "\n    int b;\n}\n",
+                            Tab);
+  Tab.UseTab = FormatStyle::UT_Never;
+  verifyWithPrefixAndSuffix("    foobar();", "\tfoobar();",
+                            "int f() {\n\tint a;\n", "\n\tint b;\n}\n", Tab);
+}
+
 TEST_F(FormatTest, CalculatesOriginalColumn) {
   EXPECT_EQ("\"qqqqqqqqqqqqqqqqqqqqqqqqqq\\\n"
             "q\"; /* some\n"