Introduce feature to search for processes (#216)

Useful for commands such as kill -STOP $pid or lsof -p $pid

Includes a preview that shows other useful information about the process selected such as parent pid, CPU use, memory use, and start time.

There will be a follow up commit to this one to clean up the code, add tests, add a gif, and enable fzf multi-select. I'm merging this in early because the PR has been open for far too long and is already in a usable, tested state.

README.md

@@ -61,6 +61,12 @@ Use `fzf.fish` to interactively find and insert different shell entities into th
 - **Remarks**
   - `$history` is excluded for technical reasons so use the search command history feature instead to inspect it
 
+### A process id
+
+- **Search input:** the pid and command of all running processes, outputted by `ps`
+- **Key binding and mnemonic:** <kbd>Ctrl</kbd>+<kbd>Alt</kbd>+<kbd>P</kbd> (`P` for process)
+- **Preview window:** the CPU usage, memory usage, start time, and other information about the process
+
 _The prompt used in the screencasts was created using [IlanCosman/tide](https://github.com/IlanCosman/tide)._
 
 ## Installation
@@ -113,6 +119,7 @@ The following variables can store custom options that will be passed to fzf by t
 | Search git log         | `fzf_git_log_opts`    |
 | Search command history | `fzf_history_opts`    |
 | Search shell variables | `fzf_shell_vars_opts` |
+| Search processes       | `fzf_processes_opts`  |
 
 They are always appended last to fzf's argument list. Because fzf uses the option appearing last when options conflict, your custom options can override hardcoded options. Custom fzf options unlocks a variety of possibilities in customizing and augmenting each feature such as:
 

conf.d/fzf.fish

@@ -6,7 +6,7 @@ end
 # Because of scoping rules, to capture the shell variables exactly as they are, we must read
 # them before even executing _fzf_search_variables. We use psub to store the
 # variables' info in temporary files and pass in the filenames as arguments.
-# # This variable is global so that it can be referenced by fzf_configure_bindings and in tests
+# This variable is global so that it can be referenced by fzf_configure_bindings and in tests
 set --global _fzf_search_vars_command '_fzf_search_variables (set --show | psub) (set --names | psub)'
 
 

functions/_fzf_configure_bindings_help.fish

@@ -12,6 +12,7 @@ DESCRIPTION
         Search git status  |  Ctrl+Alt+S (S for status)    |  --git_status
         Search history     |  Ctrl+R     (R for reverse)   |  --history
         Search variables   |  Ctrl+V     (V for variable)  |  --variables
+        Search processes   |  Ctrl+Alt+P (P for process)   |  --processes
     An option with a key sequence value overrides the binding for its feature, while an option
     without a value disables the binding. A feature that is not customized retains its default
     menomonic binding specified above. Key bindings are installed for default and insert modes.

functions/_fzf_search_processes.fish

@@ -0,0 +1,19 @@
+function _fzf_search_processes --description "Search all running processes. Replace the current token with the pid of the selected process."
+    set token (commandline --current-token)
+
+    set process_selected (
+        ps -A -opid,command | \
+        _fzf_wrapper --query "$token" \
+                     --ansi \
+                     --header-lines=1 \
+                     --preview='ps -o pid,user,ppid,%cpu,rss,time,start,command -p {1}' \
+                     $fzf_processes_opts
+    )
+
+    if test $status -eq 0
+        set pid_selected (string split --no-empty " " $process_selected)[1]
+        commandline --current-token --replace -- (string escape -- $pid_selected)
+    end
+
+    commandline --function repaint
+end

functions/fzf_configure_bindings.fish

@@ -4,7 +4,7 @@ function fzf_configure_bindings --description "Installs the default key bindings
     # no need to install bindings if not in interactive mode or running tests
     status is-interactive || test "$CI" = true; or return
 
-    set options_spec h/help 'directory=?' 'git_log=?' 'git_status=?' 'history=?' 'variables=?'
+    set options_spec h/help 'directory=?' 'git_log=?' 'git_status=?' 'history=?' 'variables=?' 'processes=?'
     argparse --max-args=0 --ignore-unknown $options_spec -- $argv 2>/dev/null
     if test $status -ne 0
         echo "Invalid option or a positional argument was provided." 1>&2
@@ -15,13 +15,14 @@ function fzf_configure_bindings --description "Installs the default key bindings
         return
     else
         # Initialize with default key sequences and then override or disable them based on flags
-        # index 1 = directory, 2 = git_log, 3 = git_status, 4 = history, 5 = variables
-        set key_sequences \e\cf \e\cl \e\cs \cr \cv # \c = control, \e = escape
+        # index 1 = directory, 2 = git_log, 3 = git_status, 4 = history, 5 = variables, 6 = processes
+        set key_sequences \e\cf \e\cl \e\cs \cr \cv \e\cp # \c = control, \e = escape
         set --query _flag_directory && set key_sequences[1] "$_flag_directory"
         set --query _flag_git_log && set key_sequences[2] "$_flag_git_log"
         set --query _flag_git_status && set key_sequences[3] "$_flag_git_status"
         set --query _flag_history && set key_sequences[4] "$_flag_history"
         set --query _flag_variables && set key_sequences[5] "$_flag_variables"
+        set --query _flag_processes && set key_sequences[6] "$_flag_processes"
 
         # If fzf bindings already exists, uninstall it first for a clean slate
         if functions --query _fzf_uninstall_bindings
@@ -34,6 +35,7 @@ function fzf_configure_bindings --description "Installs the default key bindings
             test -n $key_sequences[3] && bind --mode $mode $key_sequences[3] _fzf_search_git_status
             test -n $key_sequences[4] && bind --mode $mode $key_sequences[4] _fzf_search_history
             test -n $key_sequences[5] && bind --mode $mode $key_sequences[5] "$_fzf_search_vars_command"
+            test -n $key_sequences[6] && bind --mode $mode $key_sequences[6] _fzf_search_processes
         end
 
         function _fzf_uninstall_bindings --inherit-variable key_sequences