fix(snippets): use a correct(er) shebang

snippets/boinc.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env sh
 
 # sources:
 # - https://wiki.archlinux.org/?title=BOINC#Laptop_overheating_and_battery_duration_reduction

snippets/check port is reachable.sh

@@ -1,4 +1,4 @@
-#!sh
+#!/usr/bin/env sh
 
 # Sources:
 # - https://superuser.com/questions/621870/test-if-a-port-on-a-remote-system-is-reachable-without-telnet

snippets/diff.sh

@@ -1,4 +1,4 @@
-#!sh
+#!/usr/bin/env sh
 
 # Sources:
 # - https://stackoverflow.com/questions/8800578/how-to-colorize-diff-on-the-command-line

snippets/filesystems.sh

@@ -1,4 +1,4 @@
-#/usr/bin/env sh
+#!/usr/bin/env sh
 
 # Get the *sector* size of partitions in 512-byte sectors
 sudo blockdev --getsz '/dev/nvme0n1p1'

snippets/functions.sh

@@ -1,4 +1,4 @@
-#!sh
+#!/usr/bin/env sh
 
 is_strictly_false () {
 	if [[ "$1" =~ '0|^[Ff][Aa][Ll][Ss][Ee]$|^[Nn][Oo]?$|^$' ]]

snippets/sed.sh

@@ -1,4 +1,4 @@
-#!sh
+#!/usr/bin/env sh
 
 # Quote whatever is not a space.
 sed -E 's|([[:graph:]]+)|"\1"|g'

snippets/ssh.sh

@@ -1,3 +1,3 @@
 #!/usr/bin/env sh
 
-eval `ssh-agent` && ssh-add
+eval $(ssh-agent) && ssh-add

snippets/view files.sh

@@ -1,4 +1,4 @@
-#!sh
+#!/usr/bin/env sh
 
 # Just `vim` but read-only.
 view 'file'