Help mode documentation for ternary operator (#35637)

Co-Authored-By: Fredrik Ekre <ekrefredrik@gmail.com>

base/docs/basedocs.jl

@@ -24,7 +24,7 @@ For help on a specific function or macro, type `?` followed
 by its name, e.g. `?cos`, or `?@time`, and press enter.
 Type `;` to enter shell mode, `]` to enter package mode.
 """
-kw"help", kw"?", kw"Julia", kw"julia", kw""
+kw"help", kw"Julia", kw"julia", kw""
 
 """
     using
@@ -644,6 +644,28 @@ desired can be used.
 """
 kw"if", kw"elseif", kw"else"
 
+"""
+    a ? b : c
+
+Short form for conditionals; read "if `a`, evaluate `b` otherwise evaluate `c`".
+Also known as the [ternary operator](https://en.wikipedia.org/wiki/%3F:).
+
+This syntax is equivalent to `if a; b else c end`, but is often used to
+emphasize the value `b`-or-`c` which is being used as part of a larger
+expression, rather than the side effects that evaluating `b` or `c` may have.
+
+See the manual section on [control flow](@ref man-conditional-evaluation) for more details.
+
+# Examples
+```
+julia> x = 1; y = 2;
+
+julia> println(x > y ? "x is larger" : "y is larger")
+y is larger
+```
+"""
+kw"?", kw"?:"
+
 """
     for
 

doc/src/base/base.md

@@ -85,6 +85,7 @@ where
 ...
 ;
 =
+?:
 ```
 
 ## Standard Modules

stdlib/REPL/src/docview.jl

@@ -23,7 +23,8 @@ const extended_help_on = Ref{Any}(nothing)
 
 function _helpmode(io::IO, line::AbstractString)
     line = strip(line)
-    if startswith(line, '?')
+    ternary_operator_help = (line == "?" || line == "?:")
+    if startswith(line, '?') && !ternary_operator_help
         line = line[2:end]
         extended_help_on[] = line
         brief = false