Bump pub to the latest version.

CHANGELOG.md

Index: CHANGELOG.md
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 80077f24d9372a22e6cad03a676f4f019efe78c2..b661d40a56447aab567ab10d26e5a4f632f86d1e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,24 @@
     callback now forward stack traces along with errors to the resulting
     streams.
 
+## 1.12.1
+
+### Tool changes
+
+* Pub
+
+  * Pub will now respect `.gitignore` when validating a package before it's
+    published. For example, if a `LICENSE` file exists but is ignored, that is
+    now an error.
+
+  * If the package is in a subdirectory of a Git repository and the entire
+    subdirectory is ignored with `.gitignore`, pub will act as though nothing
+    was ignored instead of uploading an empty package.
+
+  * The heuristics for determining when `pub get` needs to be run before various
+    commands have been improved. There should no longer be false positives when
+    non-dependency sections of the pubspec have been modified.
+
 ## 1.12.0
 
 ### Language changes