Merge branch '3.2-maint'

* 3.2-maint:
  Make it harder to misinterpret semantics of boolean environment settings

diff --cc MANUAL.txt
index c1b3307760c2b1b19d795a812a63619d7b78928b,99930194b91b728b8432e28b4df6aab01871292b..6d5d8fb5aa696ef42515c309609936664c4b97ba
--- 1/MANUAL.txt
--- 2/MANUAL.txt
+++ b/MANUAL.txt
@@@ -352,10 -349,10 +352,10 @@@ WRAPPERS>>
  *extra_files_to_hash* (*CCACHE_EXTRAFILES*)::
  
      This setting is a list of paths to files that ccache will include in the
 -    the hash sum that idetifies the build. The list separator is semicolon on
 +    the hash sum that identifies the build. The list separator is semicolon on
      Windows systems and colon on other systems.
  
- *hard_link* (*CCACHE_HARDLINK*) [boolean]::
+ *hard_link* (*CCACHE_HARDLINK* or *CCACHE_NOHARDLINK*, see <<_boolean_values,Boolean values>> above)::
  
      If true, ccache will attempt to use hard links from the cache directory
      when creating the compiler output rather than using a file copy. Using hard
@@@ -375,20 -372,7 +375,20 @@@
      working directory in the debug info set incorrectly. This option is off by
      default as the incorrect setting of this debug info rarely causes problems.
      If you strike problems with GDB not using the correct directory then enable
 -    this option.
 +    this option. The option only applies when generating debug info (*-g*).
 +
 +*ignore_headers_in_manifest* (*CCACHE_IGNOREHEADERS*)::
 +
 +    This setting is a list of paths to files (or directories with headers) that
 +    ccache will *not* include in the manifest list that makes up the direct
 +    mode. Note that this can cause stale cache hits if those headers do indeed
 +    change. The list separator is semicolon on Windows systems and colon on
 +    other systems.
 +
- *keep_comments_cpp* (*CCACHE_COMMENTS*) [boolean]::
++*keep_comments_cpp* (*CCACHE_COMMENTS* or *CCACHE_NOCOMMENTS*, see <<_boolean_values,Boolean values>> above)::
 +
 +    If true, ccache will not discard the comments before hashing preprocessor
 +    output. This can be used to check documentation with *-Wdocumentation*.
  
  *log_file* (*CCACHE_LOGFILE*)::
  
@@@ -421,12 -405,7 +421,12 @@@
      <<_using_ccache_with_other_compiler_wrappers,USING CCACHE WITH OTHER
      COMPILER WRAPPERS>>.
  
- *read_only* (*CCACHE_READONLY*) [boolean]::
 +*prefix_command_cpp* (*CCACHE_PREFIX_CPP*)::
 +
 +    This option adds a list of prefixes (separated by space) to the command
 +    line that ccache uses when invoking the preprocessor.
 +
+ *read_only* (*CCACHE_READONLY* or *CCACHE_NOREADONLY*, see <<_boolean_values,Boolean values>> above)::
  
      If true, ccache will attempt to use existing cached object files, but it
      will not to try to add anything new to the cache. If you are using this

diff --cc NEWS.txt
Simple merge