- This has to be in multiple places, hence a new method. A patch failing
to apply, which is a common occurrence with HEAD builds because the
patch is already upstream, raises a different exception to another,
"normal" build failure.
Tested with:
```
╭─issyl0@rigel /home/linuxbrew/.linuxbrew/Homebrew ‹head-builds-arent-officially-supported*›
╰─ $ brew install --HEAD mtr
==> Cloning https://github.com/traviscross/mtr.git
Updating /home/issyl0/.cache/Homebrew/mtr--git
==> Checking out branch master
Already on 'master'
Your branch is up to date with 'origin/master'.
HEAD is now at 155f76a Merge pull request #340 from Sea-n/master
==> Downloading https://github.com/traviscross/mtr/pull/315.patch?full_index=1
Already downloaded: /home/issyl0/.cache/Homebrew/downloads/82d9d939303d8fceb7a3ae071ecd49a5f075e0fb451b308653b555ffbae74336--315.patch
==> Patching
==> Applying 315.patch
patching file packet/probe.c
Hunk #1 FAILED at 323.
Hunk #2 FAILED at 364.
2 out of 2 hunks FAILED -- saving rejects to file packet/probe.c.rej
Error: Failure while executing; `patch -g 0 -f -p1 -i /tmp/mtr--patch-20200330-10734-avjmyy/315.patch` exited with 1.
HEAD builds are unsupported by maintainers - please file pull requests instead of issues.
```
and
```
╭─issyl0@rigel /home/linuxbrew/.linuxbrew/Homebrew ‹head-builds-arent-officially-supported*›
╰─ $ brew install --HEAD zookeeper
==> Cloning https://gitbox.apache.org/repos/asf/zookeeper.git
Updating /home/issyl0/.cache/Homebrew/zookeeper--git
==> Checking out branch master
Already on 'master'
Your branch is up to date with 'origin/master'.
HEAD is now at 1ff1b779 ZOOKEEPER-3755: Use maven to create fatjar
==> ant compile_jute
Last 15 lines from /home/issyl0/.cache/Homebrew/Logs/zookeeper/01.ant:
2020-03-30 21:45:10 +0100
ant
compile_jute
Picked up _JAVA_OPTIONS: -Duser.home=/home/issyl0/.cache/Homebrew/java_cache
Buildfile: build.xml does not exist!
Build failed
READ THIS: https://docs.brew.sh/Troubleshooting
HEAD builds are unsupported by maintainers - please file pull requests instead of issues.
```
Don’t rely on having external commands always present in the PATH in
order to find them. Instead, provide an accessory method to Tap so
they can be added and used when needed.
While we’re here, do some general refactoring and cleanup of the
command code in these places.
