Document regex anchoring.

content/docs/operating/configuration.md

@@ -506,7 +506,7 @@ prefix is guaranteed to never be used by Prometheus itself.
 
 `<regex>` is any valid [RE2 regular
 expression](https://github.com/google/re2/wiki/Syntax). It is required for
-the `replace`, `keep`, `drop` and `labelmap` actions.
+the `replace`, `keep`, `drop` and `labelmap` actions. The regex is fully anchored.
 
 `<relabel_action>` determines the relabeling action to take:
 

content/docs/querying/basics.md

@@ -85,7 +85,7 @@ For example, this selects all `http_requests_total` time series for `staging`,
     http_requests_total{environment=~"staging|testing|development",method!="GET"}
 
 Label matchers that match empty label values also select all time series that do
-not have the specific label set at all.
+not have the specific label set at all. Regex-matches are fully anchored.
 
 Vector selectors must either specify a name or at least one label matcher
 that does not match the empty string. The following expression is illegal:

content/docs/visualization/template_reference.md

@@ -65,8 +65,8 @@ versions.
 | Name          | Arguments     | Returns |    Notes    |
 | ------------- | ------------- | ------- | ----------- |
 | title         | string        | string  | [strings.Title](http://golang.org/pkg/strings/#Title), capitalises first character of each word.|
-| match         | pattern, text | boolean | [regexp.MatchString](http://golang.org/pkg/regexp/#MatchString) Tests for a regexp match. |
-| reReplaceAll  | pattern, replacement, text | string | [Regexp.ReplaceAllString](http://golang.org/pkg/regexp/#Regexp.ReplaceAllString) Regexp substitution. |
+| match         | pattern, text | boolean | [regexp.MatchString](http://golang.org/pkg/regexp/#MatchString) Tests for a unanchored regexp match. |
+| reReplaceAll  | pattern, replacement, text | string | [Regexp.ReplaceAllString](http://golang.org/pkg/regexp/#Regexp.ReplaceAllString) Regexp substitution, unanchored. |
 | graphLink  | expr | string | Returns path to graph view in the [expression browser](/docs/visualization/browser/) for the expression. |
 | tableLink  | expr | string | Returns path to tabular ("Console") view in the [expression browser](/docs/visualization/browser/) for the expression. |