bug#51311: [PATCH] echo: update --help to document edge cases

[Florent Flament]

* src/echo.c (usage): Document edge cases when displaying arbitrary
strings with the echo command.
---
 src/echo.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/echo.c b/src/echo.c
index 18513398a..73b44660b 100644
--- a/src/echo.c
+++ b/src/echo.c
@@ -78,6 +78,14 @@ If -e is in effect, the following sequences are 
recognized:\n\
   fputs (_("\
   \\0NNN   byte with octal value NNN (1 to 3 digits)\n\
   \\xHH    byte with hexadecimal value HH (1 to 2 digits)\n\
+"), stdout);
+  fputs (_("\
+\n\
+NOTE: The echo command doesn't behave gracefully when displaying\n\
+arbitrary strings. For example, it can't display the string \"-n\" and\n\
+requires the STRICTLY_POSIX flag to display \"-e\" or \"-E\". Therefore,\n\
+if you need to display arbitrary strings please use the printf command\n\
+instead.\n\
 "), stdout);
   printf (USAGE_BUILTIN_WARNING, PROGRAM_NAME);
   emit_ancillary_info (PROGRAM_NAME);
-- 
2.25.1