Document reference commands and selective failures in the man page

README.md

@@ -89,7 +89,7 @@ hyperfine -L compiler gcc,clang '{compiler} -O2 main.cpp'
 
 ### Intermediate shell
 
-By default, commands are executed using `sh` on Unix (resolved through `PATH`) or `cmd.exe` on Windows.
+By default, commands are executed using a predefined shell (`/bin/sh` on Unix, `cmd.exe` on Windows).
 If you want to use a different shell, you can use the `-S, --shell <SHELL>` option:
 ```sh
 hyperfine --shell zsh 'for i in {1..10000}; do echo test; done'

doc/hyperfine.1

@@ -3,7 +3,8 @@
 hyperfine \- command\-line benchmarking tool
 .SH SYNOPSIS
 .B hyperfine
-.RB [ \-ihVN ]
+.RB [ \-hVN ]
+.RB [ \-\-ignore\-failure[=MODE] ]
 .RB [ \-\-warmup
 .IR NUM ]
 .RB [ \-\-min\-runs
@@ -14,6 +15,10 @@ hyperfine \- command\-line benchmarking tool
 .IR NUM ]
 .RB [ \-\-setup
 .IR CMD ]
+.RB [ \-\-reference
+.IR CMD ]
+.RB [ \-\-reference\-name
+.IR NAME ]
 .RB [ \-\-prepare
 .IR CMD ]
 .RB [ \-\-conclude
@@ -109,6 +114,16 @@ for compiling your software or with the provided parameters, or to do any
 other work that should happen once before a series of benchmark runs,
 not every time as would happen with the \fB\-\-prepare\fR option.
 .HP
+\fB\-\-reference\fR \fICMD\fP
+.IP
+Benchmark \fICMD\fP as the reference for the relative comparison of results.
+If this option is not specified, the fastest command is used as the reference.
+.HP
+\fB\-\-reference\-name\fR \fINAME\fP
+.IP
+Give a meaningful \fINAME\fP to the reference command.
+Requires \fB\-\-reference\fR.
+.HP
 \fB\-p\fR, \fB\-\-prepare\fR \fICMD...\fP
 .IP
 Execute \fICMD\fP before each timing run. This is useful for clearing disk caches,
@@ -207,9 +222,13 @@ things like "sleep 0.1; sleep 0.2" are not possible without a shell.
 .IP
 An alias for '\-\-shell=none'.
 .HP
-\fB\-i\fR, \fB\-\-ignore\-failure\fR
+\fB\-i\fR, \fB\-\-ignore\-failure\fR[=\fIMODE\fP]
 .IP
-Ignore non\-zero exit codes of the benchmarked programs.
+Ignore failures of the benchmarked programs. Without a value or with
+\fBall\-non\-zero\fR, all non\-zero exit codes are ignored.
+Alternatively, provide a comma\-separated list of exit codes to ignore,
+for example \fB\-\-ignore\-failure=1,2\fR.
+An explicit value must be attached to the option with an equals sign.
 .HP
 \fB\-\-style\fR \fITYPE\fP
 .IP