Merge pull request #242 from drm00/small-grammar-fixes

small grammar fix: it have -> it has

Author: ben

book/07-git-tools/sections/revision-selection.asc

@@ -85,7 +85,7 @@ A higher probability exists that every member of your programming team will be a
 [[_branch_references]]
 ==== Branch References
 
-The most straightforward way to specify a commit requires that it have a branch reference pointed at it.
+The most straightforward way to specify a commit requires that it has a branch reference pointed at it.
 Then, you can use a branch name in any Git command that expects a commit object or SHA-1 value.
 For instance, if you want to show the last commit object on a branch, the following commands are equivalent, assuming that the `topic1` branch points to `ca82a6d`: