doc: install --compare: clarify mode of operation

* doc/coreutils.texi (install invocation): For the --compare option,
clarify that the ownership or permissions of the source files don't
matter.  Also don't imply --owner or --group need to be specified
for --compare to be effective.
* src/install.c (usage): Add more detail on what's being compared.
Fixes https://bugs.gnu.org/50889

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index c9243c683961959c5b20d485155f2d9ed62c1f2d..8cfa698a1c3784eb1613d2b53343db951beff992 100644 (file)
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -9796,8 +9796,8 @@ The program accepts the following options.  Also see @ref{Common options}.
 @itemx --compare
 @opindex -C
 @opindex --compare
-Compare each pair of source and destination files, and if the destination has
-identical content and any specified owner, group, permissions, and possibly
+Compare content of source and destination files, and if there would be no
+change to the destination content, owner, group, permissions, and possibly
 SELinux context, then do not modify the destination at all.
 Note this option is best used in conjunction with @option{--user},
 @option{--group} and @option{--mode} options, lest @command{install}

diff --git a/src/install.c b/src/install.c
index 57a877f4a8a6a2d6e9596a0cf45c355832d4b07d..079ce1f70a38dd93791db429526cb047e77f805b 100644 (file)
--- a/src/install.c
+++ b/src/install.c
@@ -592,8 +592,9 @@ In the 4th form, create all components of the given DIRECTORY(ies).\n\
       --backup[=CONTROL]  make a backup of each existing destination file\n\
   -b                  like --backup but does not accept an argument\n\
   -c                  (ignored)\n\
-  -C, --compare       compare each pair of source and destination files, and\n\
-                        in some cases, do not modify the destination at all\n\
+  -C, --compare       compare content of source and destination files, and\n\
+                        if no change to content, ownership, and permissions,\n\
+                        do not modify the destination at all\n\
   -d, --directory     treat all arguments as directory names; create all\n\
                         components of the specified directories\n\
 "), stdout);