Update fx reference docs

Change-Id: Id232096fc5e814df2b7f140730748944d8d93f92
diff --git a/tools/fx/cmd/build.md b/tools/fx/cmd/build.md
index f229262..676d408 100644
--- a/tools/fx/cmd/build.md
+++ b/tools/fx/cmd/build.md
@@ -14,12 +14,12 @@
 If all the target arguments are `zircon/TARGET`, Fuchsia Ninja is not run.
 
 optional arguments:
-  --log LOGFILE    Print debug information to LOGFILE. Please attach the
-                   resulting file when reporting bugs.
-  --no-zircon      Skip building zircon (ignoring any zircon targets that
-                   may have been passed). This is useful for efficiently
-                   building host-side targets that have no zircon
-                   dependencies.
+  --log LOGFILE     Print debug information to LOGFILE. Please attach the
+                    resulting file when reporting bugs.
+  --no-zircon       Skip building zircon (ignoring any zircon targets that
+                    may have been passed). This is useful for efficiently
+                    building host-side targets that have no zircon
+                    dependencies.
 
 Other arguments are passed through to Ninja (same switches for both Zircon
 and Fuchsia).
diff --git a/tools/fx/cmd/emu.md b/tools/fx/cmd/emu.md
index aff54b6..45ae500 100644
--- a/tools/fx/cmd/emu.md
+++ b/tools/fx/cmd/emu.md
@@ -33,6 +33,7 @@
   --host-gpu run with host GPU acceleration
   --software-gpu run without host GPU acceleration
   --debugger pause on launch and wait for a debugger process to attach before resuming
+  --no-build do not attempt to build the fvm and zbi tools and the zbi image
 ```
 
 [emu source code](https://fuchsia.googlesource.com/fuchsia/+/HEAD/tools/devshell/emu)
diff --git a/tools/fx/cmd/fidlcat.md b/tools/fx/cmd/fidlcat.md
index 2c09e3e..b152f8a 100644
--- a/tools/fx/cmd/fidlcat.md
+++ b/tools/fx/cmd/fidlcat.md
@@ -27,7 +27,7 @@
                   [--syscalls=<regexp>] [--exclude-syscalls=<regexp>]
                   [--messages=<regexp>] [--exclude-messages=<regexp>] [--trigger=<regexp>]
                   [--dump-messages]
-                  [--verbose=<value> | --quiet=<value>] [--log-file <path>]
+                  [--verbose=<value> | --quiet=<value>] [--log-file <path>] [--stay-alive]
                   [--remote-pid=<pid>] [--remote-name=<name>] [--extra-name=<name>]
                   [run <component specification>]
 
@@ -127,6 +127,10 @@
    --quiet=<value>   The log verbosity.  Legal values are "info", "warning", "error", "fatal",
                      or a number, starting from 0. Extra verbosity comes with lower levels.
    --log-file=<path> The log file destination.
+   --stay-alive      Don't quit fidlcat when all the monitored processes have ended. This allows
+                     to keep monitoring upcoming process. At the end you have to use control-c
+                     to quit fidlcat. This is useful when you monitor a process and restart this
+                     process.
 
 Monitoring options:
    --remote-pid=<pid>    The koid of the remote process to trace.
diff --git a/tools/fx/cmd/host-tool.md b/tools/fx/cmd/host-tool.md
index 77dbfad..7564dd0 100644
--- a/tools/fx/cmd/host-tool.md
+++ b/tools/fx/cmd/host-tool.md
@@ -10,6 +10,9 @@
    --no-build       does not attempt to build the tool if it does not exist
    --check-firewall print a warning if the tool isn't included in firewall
                     rules. This is a no-op outside of macOS.
+   --print          print the tool path instead of executing it. TOOL_ARGS
+                    is ignored, but check-firewall and build behaves the
+                    same.
 
 If the tool is not known to the build system, for example if it is not in
 the GN build graph, a proper message will be printed and the script fails.
diff --git a/tools/fx/cmd/qemu.md b/tools/fx/cmd/qemu.md
index dde7a08..c64946a 100644
--- a/tools/fx/cmd/qemu.md
+++ b/tools/fx/cmd/qemu.md
@@ -5,8 +5,14 @@
 ```none
 start fuchsia in qemu with a FVM disk
 
-This command delegates to //zircon/scripts/run-zircon. Flags are documented
-in that script, and can be discovered by passing -h or --help.
+usage: fx qemu [--no-build] [-z <zbi_image>] [RUN_ZIRCON_FLAGS]
+
+     -z <zbi_image>   use <zbi_image> instead of the default.
+     --no-build       do not attempt to build the fvm and the default zbi images.
+                      A custom zbi image passed by a '-z' flag is never built.
+
+This command delegates to //zircon/scripts/run-zircon. Other flags are
+documented in that script, and can be discovered by passing -h or --help.
 
 ```
 
diff --git a/tools/fx/cmd/serve-updates.md b/tools/fx/cmd/serve-updates.md
index a3d1327..d210f7d 100644
--- a/tools/fx/cmd/serve-updates.md
+++ b/tools/fx/cmd/serve-updates.md
@@ -7,6 +7,8 @@
   -l host:port       host and port that "pm serve" will listen on
   --no-auto-config   do not configure this host as a package server on the device
   -v                 verbose mode, shows info and debug messages from "pm"
+  -C|--clean         clean the package repository first. This flag is only
+                     valid if the incremental package publishing is enabled.
 
 This command supports incremental package publishing. If enabled, it will
 auto-publish packages as they are created or modified.
diff --git a/tools/fx/cmd/serve.md b/tools/fx/cmd/serve.md
index 7ac8386..90ae3d6 100644
--- a/tools/fx/cmd/serve.md
+++ b/tools/fx/cmd/serve.md
@@ -8,6 +8,11 @@
   --no-auto-config do not configure this host as a package server on the device
   -v enable more verbose output (must be first argument)
   -a target ipv6 address for "fx pave --no-bind"
+
+NOTE: This command supports incremental package publishing. If enabled,
+it will not run 'pave' at all, and only act as a proxy for 'fx serve-updates'
+
+To enable incremental package serving, run "fx --enable=incremental serve ..."
 ```
 
 [serve source code](https://fuchsia.googlesource.com/fuchsia/+/HEAD/tools/devshell/serve)
diff --git a/tools/fx/cmd/symbolize.md b/tools/fx/cmd/symbolize.md
index dfd2ce0..8cb17c7 100644
--- a/tools/fx/cmd/symbolize.md
+++ b/tools/fx/cmd/symbolize.md
@@ -28,7 +28,7 @@
   this command.
 
   --experimental / --legacy controls which implementation to use. The default
-  is to use the legacy Go symbolizer.
+  is to use the experimental symbolizer.
 
 Authentication
 
diff --git a/tools/fx/fx.md b/tools/fx/fx.md
index 1e6b087..71db409 100644
--- a/tools/fx/fx.md
+++ b/tools/fx/fx.md
@@ -14,30 +14,24 @@
   --deprecated      Do not hide deprecated commands
 
 Global fx options: fx [OPTION]  ...
-  --dir=BUILD_DIR           Path to the build directory to use when running COMMAND.
-  -d=DEVICE[:SSH_PORT]      Target a specific device.
-                            DEVICE may be a Fuchsia device name to be resolved using
-                            device-finder or an IP address.
-                            An IPv4 address must be specified directly, while an IPv6
-                            need to be surrounded by brackets.
-                            SSH_PORT, if specified, will be used for all commands
-                            that rely on SSH to connect to the device instead of the
-                            default SSH port (22).
-                            Note: See "fx help set-device" for more help and to set
-                            the default device for a BUILD_DIR.
-  -i                        Iterative mode.  Repeat the command whenever a file is
-                            modified under your Fuchsia directory, not including
-                            out/.
-  -x                        Print commands and their arguments as they are executed.
-  -xx                       Print extra logging of the fx tool itself (implies -x)
-  --enable|disable=FEATURE  Enable or disable a feature (non-persistent). Valid features:
-      incremental
-            (default=disabled, current=disabled)
-            Packages are published and served incrementally by 'fx serve-updates'
-            as they are built. Explicit 'fx build' is not required for most operations.
-      ffx_discovery
-            (default=enabled, current=enabled)
-            Device discovery based on ffx instead of device-finder.
+  --dir=BUILD_DIR       Path to the build directory to use when running COMMAND.
+  --disable=FEATURE     Disable a feature (non-persistent).
+                        Valid values for FEATURE: []
+  -d=DEVICE[:SSH_PORT]  Target a specific device.
+                        DEVICE may be a Fuchsia device name to be resolved using
+                        device-finder or an IP address.
+                        An IPv4 address must be specified directly, while an IPv6
+                        need to be surrounded by brackets.
+                        SSH_PORT, if specified, will be used for all commands
+                        that rely on SSH to connect to the device instead of the
+                        default SSH port (22).
+                        Note: See "fx help set-device" for more help and to set
+                        the default device for a BUILD_DIR.
+  -i                    Iterative mode.  Repeat the command whenever a file is
+                        modified under your Fuchsia directory, not including
+                        out/.
+  -x                    Print commands and their arguments as they are executed.
+  -xx                   Print extra logging of the fx tool itself (implies -x)
 ```
 
 [fx source code](https://fuchsia.googlesource.com/fuchsia/+/HEAD/scripts/fx)