Sanitize and uniquify in-page anchors properly.

Things like question marks or parentheses don't play nicely in URLs in
many contexts. Replace all special characters with dashes, and also
ensure that anchors are unique within a page if there are headers with
identical texts.

content/docs/concepts/metric_types.md

@@ -63,7 +63,7 @@ during a scrape:
   * the **count** of events that have been observed, exposed as `<basename>_count` (identical to `<basename>_bucket{le="+Inf"}` above)
 
 Use the [`histogram_quantile()`
-function](/docs/querying/functions/#histogram_quantile()) to calculate
+function](/docs/querying/functions/#histogram_quantile) to calculate
 quantiles from histograms or even aggregations of histograms. A
 histogram is also suitable to calculate an [Apdex
 score](http://en.wikipedia.org/wiki/Apdex). See [histograms and

content/docs/introduction/comparison.md

@@ -74,7 +74,7 @@ geared towards slightly different use cases.
 ### Scope
 
 The same scope differences as in the case of
-[Graphite](/docs/introduction/comparison/#prometheus-vs.-graphite) apply here.
+[Graphite](/docs/introduction/comparison/#prometheus-vs-graphite) apply here.
 
 ### Data model / storage
 
@@ -139,7 +139,7 @@ node outages due to data replication.
 ### Scope
 
 The same scope differences as in the case of
-[Graphite](/docs/introduction/comparison/#prometheus-vs.-graphite) apply here.
+[Graphite](/docs/introduction/comparison/#prometheus-vs-graphite) apply here.
 
 ### Data model
 

content/docs/practices/histograms.md

@@ -91,7 +91,7 @@ calculate streaming φ-quantiles on the client side and expose them directly,
 while histograms expose bucketed observation counts and the calculation of
 quantiles from the buckets of a histogram happens on the server side using the
 [`histogram_quantile()`
-function](/docs/querying/functions/#histogram_quantile()).
+function](/docs/querying/functions/#histogram_quantile).
 
 The two approaches have a number of different implications:
 
@@ -102,8 +102,8 @@ The two approaches have a number of different implications:
 | Server performance | The server has to calculate quantiles. You can use [recording rules](/docs/querying/rules/#recording-rules) should the ad-hoc calculation take too long (e.g. in a large dashboard). | Low server-side cost.
 | Number of time series (in addition to the `_sum` and `_count` series) | One time series per configured bucket. | One time series per configured quantile.
 | Quantile error (see below for details) | Error is limited in the dimension of observed values by the width of the relevant bucket. | Error is limited in the dimension of φ by a configurable value.
-| Specification of φ-quantile and sliding time-window | Ad-hoc with [Prometheus expressions](/docs/querying/functions/#histogram_quantile()). | Preconfigured by the client.
-| Aggregation | Ad-hoc with [Prometheus expressions](/docs/querying/functions/#histogram_quantile()). | In general [not aggregatable](http://latencytipoftheday.blogspot.de/2014/06/latencytipoftheday-you-cant-average.html).
+| Specification of φ-quantile and sliding time-window | Ad-hoc with [Prometheus expressions](/docs/querying/functions/#histogram_quantile). | Preconfigured by the client.
+| Aggregation | Ad-hoc with [Prometheus expressions](/docs/querying/functions/#histogram_quantile). | In general [not aggregatable](http://latencytipoftheday.blogspot.de/2014/06/latencytipoftheday-you-cant-average.html).
 
 Note the importance of the last item in the table. Let us return to
 the SLA of serving 95% of requests within 300ms. This time, you do not
@@ -124,7 +124,7 @@ quantiles yields statistically nonsensical values.
 
 Using histograms, the aggregation is perfectly possible with the
 [`histogram_quantile()`
-function](/docs/querying/functions/#histogram_quantile()).
+function](/docs/querying/functions/#histogram_quantile).
 
     histogram_quantile(0.95, sum(rate(http_request_duration_seconds_bucket[5m])) by (le)) // GOOD.
 
@@ -223,4 +223,4 @@ summaries. Histograms are also easier to implement in a client
 library, so we recommend to implement histograms first, if in
 doubt. The reason why some libraries offer summaries but not
 histograms (the Ruby client and the legacy Java client) is that
-histograms are a more recent feature of Prometheus.
+histograms are a more recent feature of Prometheus.
\ No newline at end of file

content/docs/visualization/consoles.md

@@ -29,7 +29,7 @@ The example consoles have 5 parts:
 1. A table on the right
 
 The navigation bar is for links to other systems, such as other Prometheis
-<sup>[1](/docs/introduction/faq/#what-is-the-plural-of-prometheus?)</sup>,
+<sup>[1](/docs/introduction/faq/#what-is-the-plural-of-prometheus)</sup>,
 documentation, and whatever else makes sense to you. The menu is for navigation
 inside the same Prometheus server, which is very useful to be able to quickly
 open a console in another tab to correlate information. Both are configured in

lib/filters/add_anchors.rb

@@ -7,6 +7,7 @@ class AddAnchorsFilter < ::Nanoc::Filter
   identifier :add_anchors
 
   def run(content, params={})
+    anchors = {}
     # `#dup` is necessary because `.fragment` modifies the incoming string. Ew!
     # See https://github.com/sparklemotion/nokogiri/issues/1077
     doc = Nokogiri::HTML::DocumentFragment.parse(content.dup)
@@ -15,7 +16,22 @@ class AddAnchorsFilter < ::Nanoc::Filter
       node = Nokogiri::XML::Node.new('a', doc).tap do |a|
         a.content = ''
         a['class'] = 'header-anchor'
-        a['href'] = '#' + h_node['id']
+
+        # Replace sequences of non-word characters with single dashes. Remove
+        # extra dashes at the beginning or end.
+        anchor = h_node['id'].gsub(/\W+/, '-').gsub(/^-+|-+$/, '')
+
+        i = 0
+        unique_anchor = anchor
+        while anchors[unique_anchor] do
+          unique_anchor = "#{anchor}-#{i}"
+          i += 1
+        end
+        anchor = unique_anchor
+
+        anchors[anchor] = true
+        a['href'] = '#' + anchor
+        a['name'] = anchor
       end
       h_node.add_child(node)
     end