doc: overhaul documentation

This commit cleans up the README and splits portions of it out into
a user guide (GUIDE.md) and a FAQ (FAQ.md). The README now provides a
small list of documentation "quick" links to various parts of the docs.

This commit also does a few other minor touchups.

1 files changed, 369 insertions, 0 deletions

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+## FAQ
+
+* [Does ripgrep support configuration files?](#config)
+* [What's changed in ripgrep recently?](#changelog)
+* [When is the next release?](#release)
+* [Does ripgrep have a man page?](#manpage)
+* [Does ripgrep have support for shell auto-completion?](#complete)
+* [How do I use lookaround and/or backreferences?](#fancy)
+* [How do I stop ripgrep from messing up colors when I kill it?](#stop-ripgrep)
+* [How can I get results in a consistent order?](#order)
+* [How do I search files that aren't UTF-8?](#encoding)
+* [How do I search compressed files?](#compressed)
+* [How do I search over multiple lines?](#multiline)
+* [How do I get around the regex size limit?](#size-limit)
+* [How do I make the `-f/--file` flag faster?](#dfa-size)
+* [How do I make the output look like The Silver Searcher's output?](#silver-searcher-output)
+* [When I run `rg`, why does it execute some other command?](#rg-other-cmd)
+* [How do I create an alias for ripgrep on Windows?](#rg-alias-windows)
+* [How do I create a PowerShell profile?](#powershell-profile)
+* [How do I pipe non-ASCII content to ripgrep on Windows?](#pipe-non-ascii-windows)
+
+
+<h3 name="config">
+Does ripgrep support configuration files?
+</h3>
+
+Yes. See the [guide's section on configuration files](#configuration-file).
+
+
+<h3 name="changelog">
+What's changed in ripgrep recently?
+</h3>
+
+Please consult ripgrep's [CHANGELOG](CHANGELOG.md).
+
+
+<h3 name="release">
+When is the next release?
+</h3>
+
+ripgrep is a project whose contributors are volunteers. A release schedule
+adds undue stress to said volunteers. Therefore, releases are made on a best
+effort basis and no dates **will ever be given**.
+
+One exception to this is high impact bugs. If a ripgrep release contains a
+significant regression, then there will generally be a strong push to get a
+patch release out with a fix.
+
+
+<h3 name="manpage">
+Does ripgrep have a man page?
+</h3>
+
+Yes! Whenever ripgrep is compiled on a system with `asciidoc` present, then a
+man page is generated from ripgrep's argv parser. After compiling ripgrep, you
+can find the man page like so from the root of the repository:
+
+```
+$ find ./target -name rg.1 -print0 | xargs -0 ls -t | head -n1
+./target/debug/build/ripgrep-79899d0edd4129ca/out/rg.1
+```
+
+Running `man -l ./target/debug/build/ripgrep-79899d0edd4129ca/out/rg.1` will
+show the man page in your normal pager.
+
+Note that the man page's documentation for options is equivalent to the output
+shown in `rg --help`. To see more condensed documentation (one line per flag),
+run `rg -h`.
+
+The man page is also included in all
+[ripgrep binary releases](https://github.com/BurntSushi/ripgrep/releases).
+
+
+<h3 name="complete">
+Does ripgrep have support for shell auto-completion?
+</h3>
+
+Yes! Shell completions can be found in the
+[same directory as the man page](#manpage)
+after building ripgrep. Zsh completions are maintained separately and committed
+to the repository in `complete/_rg`.
+
+Shell completions are also included in all
+[ripgrep binary releases](https://github.com/BurntSushi/ripgrep/releases).
+
+For **bash**, move `rg.bash` to
+`$XDG_CONFIG_HOME/bash_completion` or `/etc/bash_completion.d/`.
+
+For **fish**, move `rg.fish` to `$HOME/.config/fish/completions/`.
+
+For **zsh**, move `_rg` to one of your `$fpath` directories.
+
+For **PowerShell**, add `. _rg.ps1` to your PowerShell
+[profile](https://technet.microsoft.com/en-us/library/bb613488(v=vs.85).aspx)
+(note the leading period). If the `_rg.ps1` file is not on your `PATH`, do
+`. /path/to/_rg.ps1` instead.
+
+
+<h3 name="order">
+How can I get results in a consistent order?
+</h3>
+
+By default, ripgrep uses parallelism to execute its search because this makes
+the search much faster on most modern systems. This in turn means that ripgrep
+has a non-deterministic aspect to it, since the interleaving of threads during
+the execution of the program is itself non-deterministic. This has the effect
+of printing results in a somewhat arbitrary order, and this order can change
+from run to run of ripgrep.
+
+The only way to make the order of results consistent is to ask ripgrep to
+sort the output. Currently, this will disable all parallelism. (On smaller
+repositories, you might not notice much of a performance difference!) You
+can achieve this with the `--sort-files` flag.
+
+There is more discussion on this topic here:
+https://github.com/BurntSushi/ripgrep/issues/152
+
+
+<h3 name="encoding">
+How do I search files that aren't UTF-8?
+</h3>
+
+See the [guide's section on file encoding](GUIDE.md#file-encoding).
+
+
+<h3 name="compressed">
+How do I search compressed files?
+</h3>
+
+ripgrep's `-z/--search-zip` flag will cause it to search compressed files
+automatically. Currently, this supports gzip, bzip2, lzma and xz only and
+requires the corresponding `gzip`, `bzip2` and `xz` binaries to be installed on
+your system. (That is, ripgrep does decompression by shelling out to another
+process.)
+
+ripgrep currently does not search archive formats, so `*.tar.gz` files, for
+example, are skipped.
+
+
+<h3 name="multiline">
+How do I search over multiple lines?
+</h3>
+
+This isn't currently possible. ripgrep is fundamentally a line-oriented search
+tool. With that said,
+[multiline search is a planned opt-in feature](https://github.com/BurntSushi/ripgrep/issues/176).
+
+
+<h3 name="fancy">
+How do I use lookaround and/or backreferences?
+</h3>
+
+This isn't currently possible. ripgrep uses finite automata to implement
+regular expression search, and in turn, guarantees linear time searching on all
+inputs. It is difficult to efficiently support lookaround and backreferences in
+finite automata engines, so ripgrep does not provide these features.
+
+If a production quality regular expression engine with these features is ever
+written in Rust, then it is possible ripgrep will provide it as an opt-in
+feature.
+
+
+<h3 name="stop-ripgrep">
+How do I stop ripgrep from messing up colors when I kill it?
+</h3>
+
+Type in `color` in cmd.exe (Command Prompt) and `echo -ne "\033[0m"` on
+Unix-like systems to restore your original foreground color.
+
+In PowerShell, you can add the following code to your profile which will
+restore the original foreground color when `Reset-ForegroundColor` is called.
+Including the `Set-Alias` line will allow you to call it with simply `color`.
+
+```powershell
+$OrigFgColor = $Host.UI.RawUI.ForegroundColor
+function Reset-ForegroundColor {
+	$Host.UI.RawUI.ForegroundColor = $OrigFgColor
+}
+Set-Alias -Name color -Value Reset-ForegroundColor
+```
+
+PR [#187](https://github.com/BurntSushi/ripgrep/pull/187) fixed this, and it
+was later deprecated in
+[#281](https://github.com/BurntSushi/ripgrep/issues/281). A full explanation is
+available
+[here](https://github.com/BurntSushi/ripgrep/issues/281#issuecomment-269093893).
+
+
+<h3 name="size-limit">
+How do I get around the regex size limit?
+</h3>
+
+If you've given ripgrep a particularly large pattern (or a large number of
+smaller patterns), then it is possible that it will fail to compile because it
+hit a pre-set limit. For example:
+
+```
+$ rg '\pL{1000}'
+Compiled regex exceeds size limit of 10485760 bytes.
+```
+
+(Note: `\pL{1000}` may look small, but `\pL` is the character class containing
+all Unicode letters, which is quite large. *And* it's repeated 1000 times.)
+
+In this case, you can work around by simply increasing the limit:
+
+```
+$ rg '\pL{1000}' --regex-size-limit 1G
+```
+
+Increasing the limit to 1GB does not necessarily mean that ripgrep will use
+that much memory. The limit just says that it's allowed to (approximately) use
+that much memory for constructing the regular expression.
+
+
+<h3 name="dfa-size">
+How do I make the <code>-f/--file</code> flag faster?
+</h3>
+
+The `-f/--file` permits one to give a file to ripgrep which contains a pattern
+on each line. ripgrep will then report any line that matches any of the
+patterns.
+
+If this pattern file gets too big, then it is possible ripgrep will slow down
+dramatically. *Typically* this is because an internal cache is too small, and
+will cause ripgrep to spill over to a slower but more robust regular expression
+engine. If this is indeed the problem, then it is possible to increase this
+cache and regain speed. The cache can be controlled via the `--dfa-size-limit`
+flag. For example, using `--dfa-size-limit 1G` will set the cache size to 1GB.
+(Note that this doesn't mean ripgrep will use 1GB of memory automatically, but
+it will allow the regex engine to if it needs to.)
+
+
+<h3 name="silver-searcher-output">
+How do I make the output look like The Silver Searcher's output?
+</h3>
+
+Use the `--colors` flag, like so:
+
+```
+rg --colors line:fg:yellow      \
+   --colors line:style:bold     \
+   --colors path:fg:green       \
+   --colors path:style:bold     \
+   --colors match:fg:black      \
+   --colors match:bg:yellow     \
+   --colors match:style:nobold  \
+   foo
+```
+
+Alternatively, add your color configuration to your ripgrep config file (which
+is activated by setting the `RIPGREP_CONFIG_PATH` environment variable to point
+to your config file). For example:
+
+```
+$ cat $HOME/.config/ripgrep/rc
+--colors=line:fg:yellow
+--colors=line:style:bold
+--colors=path:fg:green
+--colors=path:style:bold
+--colors=match:fg:black
+--colors=match:bg:yellow
+--colors=match:style:nobold
+$ RIPGREP_CONFIG_PATH=$HOME/.config/ripgrep/rc rg foo
+```
+
+
+<h3 name="rg-other-cmd">
+When I run <code>rg</code>, why does it execute some other command?
+</h3>
+
+It's likely that you have a shell alias or even another tool called `rg` which
+is interfering with ripgrep. Run `which rg` to see what it is.
+
+(Notably, the Rails plug-in for
+[Oh My Zsh](https://github.com/robbyrussell/oh-my-zsh/wiki/Plugins#rails) sets
+up an `rg` alias for `rails generate`.)
+
+Problems like this can be resolved in one of several ways:
+
+* If you're using the OMZ Rails plug-in, disable it by editing the `plugins`
+  array in your zsh configuration.
+* Temporarily bypass an existing `rg` alias by calling ripgrep as
+  `command rg`, `\rg`, or `'rg'`.
+* Temporarily bypass an existing alias or another tool named `rg` by calling
+  ripgrep by its full path (e.g., `/usr/bin/rg` or `/usr/local/bin/rg`).
+* Permanently disable an existing `rg` alias by adding `unalias rg` to the
+  bottom of your shell configuration file (e.g., `.bash_profile` or `.zshrc`).
+* Give ripgrep its own alias that doesn't conflict with other tools/aliases by
+  adding a line like the following to the bottom of your shell configuration
+  file: `alias ripgrep='command rg'`.
+
+
+<h3 name="rg-alias-windows">
+How do I create an alias for ripgrep on Windows?
+</h3>
+
+Often you can find a need to make alias for commands you use a lot that set
+certain flags. But PowerShell function aliases do not behave like your typical
+linux shell alias. You always need to propagate arguments and `stdin` input.
+But it cannot be done simply as
+`function grep() { $input | rg.exe --hidden $args }`
+
+Use below example as reference to how setup alias in PowerShell.
+
+```powershell
+function grep {
+    $count = @($input).Count
+    $input.Reset()
+
+    if ($count) {
+        $input | rg.exe --hidden $args
+    }
+    else {
+        rg.exe --hidden $args
+    }
+}
+```
+
+PowerShell special variables:
+
+* input - is powershell `stdin` object that allows you to access its content.
+* args - is array of arguments passed to this function.
+
+This alias checks whether there is `stdin` input and propagates only if there
+is some lines. Otherwise empty `$input` will make powershell to trigger `rg` to
+search empty `stdin`.
+
+
+<h3 name="powershell-profile">
+How do I create a PowerShell profile?
+</h3>
+
+To customize powershell on start-up, there is a special PowerShell script that
+has to be created. In order to find its location, type `$profile`.
+See
+[Microsoft's documentation](https://technet.microsoft.com/en-us/library/bb613488(v=vs.85).aspx)
+for more details.
+
+Any PowerShell code in this file gets evaluated at the start of console. This
+way you can have own aliases to be created at start.
+
+
+<h3 name="pipe-non-ascii-windows">
+How do I pipe non-ASCII content to ripgrep on Windows?
+</h3>
+
+When piping input into native executables in PowerShell, the encoding of the
+input is controlled by the `$OutputEncoding` variable. By default, this is set
+to US-ASCII, and any characters in the pipeline that don't have encodings in
+US-ASCII are converted to `?` (question mark) characters.
+
+To change this setting, set `$OutputEncoding` to a different encoding, as
+represented by a .NET encoding object. Some common examples are below. The
+value of this variable is reset when PowerShell restarts, so to make this
+change take effect every time PowerShell is started add a line setting the
+variable into your PowerShell profile.
+
+Example `$OutputEncoding` settings:
+
+* UTF-8 without BOM: `$OutputEncoding = [System.Text.UTF8Encoding]::new()`
+* The console's output encoding:
+  `$OutputEncoding = [System.Console]::OutputEncoding`
+
+If you continue to have encoding problems, you can also force the encoding
+that the console will use for printing to UTF-8 with
+`[System.Console]::OutputEncoding = [System.Text.Encoding]::UTF8`. This
+will also reset when PowerShell is restarted, so you can add that line
+to your profile as well if you want to make the setting permanent.