gtfmt 
Like go fmt but for go templates.
Due to several problems found in round-tripping templates through the stdlib parser and lexer, use of this command should be considered experimental. See the bugs section below.
Rewriting with -r is still experimental and should be used with extreme caution, as it may have unintended consequences.
Bugs
Whitespace deletion(i.e. {{- "foo" -}}) gets formatted into actually deleting the whitespace. While this technically doesn't change the output of your template, it is effectively "destructive" to the template, since you can't just remove a dash if you don't like the effect of the whitespace deletion.
sub-templates (i.e. {{define "foo"}}) are currently not supported
(gtfmt will refuse to run on templates that use subtemplates).
Template comments are stripped when formatting.
Examples
$ echo 'Hi! {{ foo .Index.Bar "byte" }}33' | gtfmt
Hi! {{foo .Index.Bar "byte"}}33
// replace a function name
$ echo 'Hi! {{ Foo .Index.Foo "Foo" }}33' | gtfmt -r 'Foo -> Baz'
Hi! {{Baz .Index.Foo "Foo"}}33
// replace a field's path
$ echo 'Hi! {{ Foo .Index.Foo "Foo" }}33' | gtfmt -r '.Index.Foo -> .Index.Baz.Foo'
Hi! {{Baz .Index.Baz.Foo "Foo"}}33
Usage
usage: gtfmt [options] [file1] <[file2]...>
Reformats one or more go templates. If not given a filename, will read from stdin.
Options:
-l list templates that would be updated (but don't update them)
-r string
rewrite rule e.g. '.Foo.Bar -> .Foo.Baz.Bar'
Rewrite rules:
** this is still in alpha and subject to change **
** use with extreme caution **
* Replace all or part of a path with another path:
.Index.Foo -> .Index.Baz.Foo
The paths *must* start with a ".". Matching is case sensitive, on full words only.
* Replace a function with another function:
foo -> bar
The lack of a . indicates this is a function replacement.