Build tags allow different implementations of code sections to be
included in the binary, so can be important to understand the exact
behaviour expected at runtime.

This change includes build tags at the end of the `BuildContext` string,
and as an extra label on the info metric.

Signed-off-by: Bryan Boreham <[email protected]>

Signed-off-by: Bryan Boreham <[email protected]>

Without using a regexp.

Code inspired by Go standard library `time.ParseDuration`, but
simplified and supporting different units.

Signed-off-by: Bryan Boreham <[email protected]>

Parse Durations much faster

version: add Go build tags to output

This commit adds a new field `ProxyFromEnvironment` to the
`HTTPClientConfig` and `OAuth2` structs to enable Prometheus to use the
default proxy from the environment variable (as specified in net/http
ProxyFromEnvironment.) This is opt-out by default, so does not change
anything for existing users.

This change is necessary because Prometheus previously had insufficient
behavior to avoid proxying EC2 metadata requests when `proxy_url` is
set in `ec2_sd_configs`.

This commit also adds the ability to support `no_proxy`.

See prometheus/prometheus#11991

Signed-off-by: Julien Pivotto <[email protected]>

Add support to use Proxy From Environment