doc: more semicolons instead of periods in option descriptions

Also slightly rephrase some descriptions for extra clarity, and
add more consistent indentation.

* src/df.c (usage): Semicolon, no final period.
* src/du.c (usage): Likewise, plus indentation and clarifying words.
* src/ls.c (usage): Semicolon, rephrasings, added parentheses for
clarity, indentation.
* src/rm.c (usage): Semicolons.
* src/tail.c (usage): Adjust -f description to prefer explanatory
language instead of option syntax.

5 files changed, 36 insertions, 32 deletions

diff --git a/src/df.c b/src/df.c
index e01806490..c2c390e3a 100644
--- a/src/df.c
+++ b/src/df.c
@@ -1233,9 +1233,9 @@ or all file systems by default.\n\
 
       fputs (_("\
   -a, --all             include dummy file systems\n\
-  -B, --block-size=SIZE  scale sizes by SIZE before printing them.  E.g.,\n\
-                           '-BM' prints sizes in units of 1,048,576 bytes.\n\
-                           See SIZE format below.\n\
+  -B, --block-size=SIZE  scale sizes by SIZE before printing them; e.g.,\n\
+                           '-BM' prints sizes in units of 1,048,576 bytes;\n\
+                           see SIZE format below\n\
       --total           produce a grand total\n\
   -h, --human-readable  print sizes in human readable format (e.g., 1K 234M 2G)\
 \n\
diff --git a/src/du.c b/src/du.c
index b8aba0b32..a265b10ba 100644
--- a/src/du.c
+++ b/src/du.c
@@ -298,9 +298,9 @@ Summarize disk usage of each FILE, recursively for directories.\n\
                           fragmentation, indirect blocks, and the like\n\
 "), stdout);
       fputs (_("\
-  -B, --block-size=SIZE  scale sizes by SIZE before printing them.  E.g.,\n\
-                           '-BM' prints sizes in units of 1,048,576 bytes.\n\
-                           See SIZE format below.\n\
+  -B, --block-size=SIZE  scale sizes by SIZE before printing them; e.g.,\n\
+                           '-BM' prints sizes in units of 1,048,576 bytes;\n\
+                           see SIZE format below\n\
   -b, --bytes           equivalent to '--apparent-size --block-size=1'\n\
   -c, --total           produce a grand total\n\
   -D, --dereference-args  dereference only symlinks that are listed on the\n\
@@ -338,9 +338,9 @@ Summarize disk usage of each FILE, recursively for directories.\n\
                           directory, or any of its subdirectories\n\
       --time=WORD       show time as WORD instead of modification time:\n\
                           atime, access, use, ctime or status\n\
-      --time-style=STYLE  show times using style STYLE:\n\
-                          full-iso, long-iso, iso, +FORMAT\n\
-                          FORMAT is interpreted like 'date'\n\
+      --time-style=STYLE  show times using STYLE, which can be:\n\
+                            full-iso, long-iso, iso, or +FORMAT;\n\
+                            FORMAT is interpreted like in 'date'\n\
 "), stdout);
       fputs (_("\
   -X, --exclude-from=FILE  exclude files that match any pattern in FILE\n\
diff --git a/src/ls.c b/src/ls.c
index f3c3a1b82..1652bcf94 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -4769,10 +4769,10 @@ Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.\n\
 "), stdout);
       fputs (_("\
   -C                         list entries by columns\n\
-      --color[=WHEN]         colorize the output.  WHEN defaults to 'always'\n\
-                               or can be 'never' or 'auto'; more info below\n\
-  -d, --directory            list directory entries instead of contents,\n\
-                               and do not dereference symbolic links\n\
+      --color[=WHEN]         colorize the output; WHEN can be 'never', 'auto',\
+\n\
+                               or 'always' (the default); more info below\n\
+  -d, --directory            list directories themselves, not their contents\n\
   -D, --dired                generate output designed for Emacs' dired mode\n\
 "), stdout);
       fputs (_("\
@@ -4835,9 +4835,10 @@ Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.\n\
                              append / indicator to directories\n\
 "), stdout);
       fputs (_("\
-  -q, --hide-control-chars   print ? instead of non-graphic characters\n\
-      --show-control-chars   show non graphic characters as-is (default\n\
-                             unless program is 'ls' and output is a terminal)\n\
+  -q, --hide-control-chars   print ? instead of nongraphic characters\n\
+      --show-control-chars   show nongraphic characters as-is (the default,\n\
+                               unless program is 'ls' and output is a terminal)\
+\n\
   -Q, --quote-name           enclose entry names in double quotes\n\
       --quoting-style=WORD   use quoting style WORD for entry names:\n\
                                literal, locale, shell, shell-always, c, escape\
@@ -4850,22 +4851,25 @@ Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.\n\
 "), stdout);
       fputs (_("\
   -S                         sort by file size\n\
-      --sort=WORD            sort by WORD instead of name: none -U,\n\
-                             extension -X, size -S, time -t, version -v\n\
-      --time=WORD            with -l, show time as WORD instead of modification\
-\n\
-                             time: atime -u, access -u, use -u, ctime -c,\n\
-                             or status -c; use specified time as sort key\n\
-                             if --sort=time\n\
+      --sort=WORD            sort by WORD instead of name: none (-U), size (-S)\
+,\n\
+                               time (-t), version (-v), extension (-X)\n\
+      --time=WORD            with -l, show time as WORD instead of default\n\
+                               modification time: atime or access or use (-u)\n\
+                               ctime or status (-c); also use specified time\n\
+                               as sort key if --sort=time\n\
 "), stdout);
       fputs (_("\
       --time-style=STYLE     with -l, show times using style STYLE:\n\
-                             full-iso, long-iso, iso, locale, +FORMAT;\n\
-                             FORMAT is interpreted like 'date'; if FORMAT is\n\
-                             FORMAT1<newline>FORMAT2, then FORMAT1 applies to\n\
-                             non-recent files and FORMAT2 to recent files;\n\
-                             if STYLE is prefixed with 'posix-', STYLE\n\
-                             takes effect only outside the POSIX locale\n\
+                               full-iso, long-iso, iso, locale, or +FORMAT;\n\
+                               FORMAT is interpreted like in 'date'; if FORMAT\
+\n\
+                               is FORMAT1<newline>FORMAT2, then FORMAT1 applies\
+\n\
+                               to non-recent files and FORMAT2 to recent files;\
+\n\
+                               if STYLE is prefixed with 'posix-', STYLE\n\
+                               takes effect only outside the POSIX locale\n\
 "), stdout);
       fputs (_("\
   -t                         sort by modification time, newest first\n\
diff --git a/src/rm.c b/src/rm.c
index b9b84e117..4b87c12e8 100644
--- a/src/rm.c
+++ b/src/rm.c
@@ -141,10 +141,10 @@ Remove (unlink) the FILE(s).\n\
 "), stdout);
       fputs (_("\
   -I                    prompt once before removing more than three files, or\n\
-                          when removing recursively.  Less intrusive than -i,\n\
+                          when removing recursively; less intrusive than -i,\n\
                           while still giving protection against most mistakes\n\
       --interactive[=WHEN]  prompt according to WHEN: never, once (-I), or\n\
-                          always (-i).  Without WHEN, prompt always\n\
+                          always (-i); without WHEN, prompt always\n\
 "), stdout);
       fputs (_("\
       --one-file-system  when removing a hierarchy recursively, skip any\n\
diff --git a/src/tail.c b/src/tail.c
index 8389467b4..e7fefda71 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -274,7 +274,7 @@ With no FILE, or when FILE is -, read standard input.\n\
      fputs (_("\
   -f, --follow[={name|descriptor}]\n\
                            output appended data as the file grows;\n\
-                             -f and --follow[=descriptor] are equivalent\n\
+                             an absent option argument means 'descriptor'\n\
   -F                       same as --follow=name --retry\n\
 "), stdout);
      printf (_("\