gdb/doc: document how filename arguments are formatted

In the following commits I intend to improve GDB's filename
completion.  However, how filenames should be completed is a little
complex because GDB is not consistent with how it expects filename
arguments to be formatted.

This commit documents the current state of GDB when it comes to
formatting filename arguments.

Currently GDB will not correctly complete filenames inline with this
documentation; GDB will either fail to complete, or complete
incorrectly (i.e. the result of completion will not then be accepted
by GDB).  However, later commits in this series will fix completion.

Approved-By: Eli Zaretskii <eliz@gnu.org>

gdb/doc/gdb.texinfo

@@ -1752,6 +1752,7 @@ show you the alternatives available, if there is more than one possibility).
 * Command Syntax::              How to give commands to @value{GDBN}
 * Command Settings::            How to change default behavior of commands
 * Completion::                  Command completion
+* Filename Arguments::		Filenames As Command Arguments
 * Command Options::             Command options
 * Help::                        How to ask @value{GDBN} for help
 @end menu
@@ -2123,6 +2124,68 @@ struct ui_file
 @}
 @end smallexample
 
+@node Filename Arguments
+@section Filenames As Command Arguments
+@cindex file names, quoting and escaping
+
+When passing filenames (or directory names) as arguments to a command,
+if the filename argument does not include any whitespace, double
+quotes, or single quotes, then for all commands the filename can be
+written as a simple string, for example:
+
+@smallexample
+(@value{GDBP}) file /path/to/some/file
+@end smallexample
+
+If the filename does include whitespace, double quotes, or single
+quotes, then @value{GDBN} has two approaches for how these filenames
+should be formatted; which format to use depends on which command is
+being used.
+
+Most @value{GDBN} commands don't require, or support, quoting and
+escaping.  These commands treat any text after the command name, that
+is not a command option (@pxref{Command Options}), as the filename,
+even if the filename contains whitespace or quote characters.  In the
+following example the user is adding @w{@file{/path/that contains/two
+spaces/}} to the auto-load safe-path (@pxref{add-auto-load-safe-path}):
+
+@smallexample
+(@value{GDBP}) add-auto-load-safe-path /path/that contains/two spaces/
+@end smallexample
+
+A small number of commands require that filenames containing
+whitespace or quote characters are either quoted, or have the special
+characters escaped with a backslash.  Commands that support this style
+are marked as such in the manual, any command not marked as accepting
+quoting and escaping of its filename argument, does not accept this
+filename argument style.
+
+For example, to load the file @w{@file{/path/with spaces/to/a file}}
+with the @code{file} command (@pxref{Files, ,Commands to Specify
+Files}), you can escape the whitespace characters with a backslash:
+
+@smallexample
+(@value{GDBP}) file /path/with\ spaces/to/a\ file
+@end smallexample
+
+Alternatively the entire filename can be wrapped in either single or
+double quotes, in which case no backlsashes are needed, for example:
+
+@smallexample
+(@value{GDBP}) symbol-file "/path/with spaces/to/a file"
+(@value{GDBP}) exec-file '/path/with spaces/to/a file'
+@end smallexample
+
+It is possible to include a quote character within a quoted filename
+by escaping it with a backslash, for example, within a filename
+surrounded by double quotes, a double quote character should be
+escaped with a backslash, but a single quote character should not be
+escaped.  Within a single quoted string a single quote character needs
+to be escaped, but a double quote character does not.
+
+A literal backslash character can also be included by escaping it with
+a backslash.
+
 @node Command Options
 @section Command options
 
@@ -21615,6 +21678,9 @@ directories to search, just as the shell does when looking for a program
 to run.  You can change the value of this variable, for both @value{GDBN}
 and your program, using the @code{path} command.
 
+The @var{filename} argument supports escaping and quoting, see
+@ref{Filename Arguments,,Filenames As Command Arguments}.
+
 @cindex unlinked object files
 @cindex patching object files
 You can load unlinked object @file{.o} files into @value{GDBN} using
@@ -21637,6 +21703,9 @@ in @var{filename}.  @value{GDBN} searches the environment variable @env{PATH}
 if necessary to locate your program.  Omitting @var{filename} means to
 discard information on the executable file.
 
+The @var{filename} argument supports escaping and quoting, see
+@ref{Filename Arguments,,Filenames As Command Arguments}.
+
 @kindex symbol-file
 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
 Read symbol table information from file @var{filename}.  @env{PATH} is
@@ -21660,6 +21729,9 @@ which are part of the old symbol table data being discarded inside
 @code{symbol-file} does not repeat if you press @key{RET} again after
 executing it once.
 
+The @var{filename} argument supports escaping and quoting, see
+@ref{Filename Arguments,,Filenames As Command Arguments}.
+
 When @value{GDBN} is configured for a particular environment, it
 understands debugging information in whatever format is the standard
 generated for that environment; you may use either a @sc{gnu} compiler, or
@@ -21754,6 +21826,9 @@ originally read with the @code{symbol-file} command.  You can use the
 @code{add-symbol-file} command any number of times; the new symbol data
 thus read is kept in addition to the old.
 
+The @var{filename} argument supports escaping and quoting, see
+@ref{Filename Arguments,,Filenames As Command Arguments}.
+
 Changes can be reverted using the command @code{remove-symbol-file}.
 
 @cindex relocatable object files, reading symbols from
@@ -21813,6 +21888,9 @@ Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
 
 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
 
+The @var{filename} argument supports escaping and quoting, see
+@ref{Filename Arguments,,Filenames As Command Arguments}.
+
 @kindex add-symbol-file-from-memory
 @cindex @code{syscall DSO}
 @cindex load symbols from memory