Allow cygwin_conv_path(3) and cygpath(1) to emit /proc/cygdrive prefixed path

        * include/sys/cygwin.h (CCP_PROC_CYGDRIVE): New flag.
        * mount.cc (mount_info::cygdrive_posix_path): Take flag values rather
        than just a trailing_slash_p bool.  Emit /proc/cygdrive path if
        CCP_PROC_CYGDRIVE flag is given.
        (mount_info::conv_to_posix_path): Take flag values rather than just
        a keep_rel_p bool.  Rename _p variables.  Print flag value as hex in
        debug_printf.  Call cygdrive_posix_path with flag values.
        * mount.h (mount_info::cygdrive_posix_path): Accommodate above change
        in declaration.
        (mount_info::conv_to_posix_path): Ditto.
        * fhandler_process.cc (format_process_exename): Accommodate change to
        mount_info::conv_to_posix_path.
        * path.cc (cygwin_conv_path): Ditto.

        * cygpath.cc (absolute_flag): Initialize to CCP_RELATIVE to simplify
        expressions.
        (cygdrive_flag): New global flag.
        (long_options): Add --proc-cygdrive option.
        (options): Add -U option.
        (usage): Add description for -U option.
        (do_sysfolders): Or cygdrive_flag to cygwin_conv_path call.
        (do_pathconv): Simply or absolute_flag to conv_func.  Or
        cygdrive_flag to conv_func.
        (do_options): Initalize absolute_flag to CCP_RELATIVE.  Initialize new
        cygdrive_flag.  Set absolute_flag to CCP_ABSOLUTE on -a.  Set
        cygdrive_flag to CCP_PROC_CYGDRIVE on -U.

        * new-features.xml (ov-new2.4): Document cygpath -U option.
        * utils.xml (cygpath): Ditto.
        * path.xml (func-cygwin-path): Add CCP_PROC_CYGDRIVE description.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

4 files changed, 27 insertions, 2 deletions

diff --git a/winsup/doc/ChangeLog b/winsup/doc/ChangeLog
index e5477cee2..f9ae2b54e 100644
--- a/winsup/doc/ChangeLog
+++ b/winsup/doc/ChangeLog
@@ -1,3 +1,9 @@
+2015-12-06  Corinna Vinschen  <corinna@vinschen.de>
+
+	* new-features.xml (ov-new2.4): Document cygpath -U option.
+	* utils.xml (cygpath): Ditto.
+	* path.xml (func-cygwin-path): Add CCP_PROC_CYGDRIVE description.
+
 2015-11-25  David Macek  <david.macek.0@gmail.com>
 
 	* faq-using.xml: Add MacType to the BLODA.  Fix formatting.
diff --git a/winsup/doc/new-features.xml b/winsup/doc/new-features.xml
index 21bc6911f..98a9e6c14 100644
--- a/winsup/doc/new-features.xml
+++ b/winsup/doc/new-features.xml
@@ -32,6 +32,11 @@ created by Cygwin processes.
 </para></listitem>
 
 <listitem><para>
+cygpath has a new -U option, which creates cygdrive paths using the
+unambiguous /proc/cygdrive prefix.
+</para></listitem>
+
+<listitem><para>
 New API: rpmatch.
 </para></listitem>
 
diff --git a/winsup/doc/path.xml b/winsup/doc/path.xml
index bea67980a..81d4c3f35 100644
--- a/winsup/doc/path.xml
+++ b/winsup/doc/path.xml
@@ -54,8 +54,10 @@ relative paths in relative notation.  Creating absolute paths is the
 default.</para>
 
 <programlisting>
-  CCP_ABSOLUTE = 0,       /* Request absolute path (default).             */
-  CCP_RELATIVE = 0x100    /* Request to keep path relative.               */
+  CCP_ABSOLUTE = 0,         /* Request absolute path (default).             */
+  CCP_RELATIVE = 0x100      /* Request to keep path relative.               */
+  CCP_PROC_CYGDRIVE = 0x200 /* Request to return /proc/cygdrive path
+                               (only with CCP_*_TO_POSIX).                  */
 </programlisting>
 
 <para><parameter>size</parameter> is the size of the buffer pointed to
diff --git a/winsup/doc/utils.xml b/winsup/doc/utils.xml
index f48bfaec0..d0f871efe 100644
--- a/winsup/doc/utils.xml
+++ b/winsup/doc/utils.xml
@@ -315,6 +315,8 @@ Path conversion options:
   -a, --absolute        output absolute path
   -l, --long-name       print Windows long form of NAMEs (with -w, -m only)
   -p, --path            NAME is a PATH list (i.e., '/bin:/usr/bin')
+  -U, --proc-cygdrive   Emit /proc/cygdrive path instead of cygdrive prefix
+                        when converting Windows path to UNIX path.
   -s, --short-name      print DOS (short) form of NAMEs (with -w, -m only)
   -C, --codepage CP     print DOS, Windows, or mixed pathname in Windows
                         codepage CP.  CP can be a numeric codepage identifier,
@@ -380,6 +382,16 @@ Other options:
       graphical tools like Windows Explorer might expect pathnames in the
       current ANSI codepage.</para>
 
+    <para>The <literal>-U</literal> option allows to use cygpath to create
+    unambiguous Unix paths pointing outside the Cygwin tree andf thus having
+    no explicit POSIX path.  Those paths usually use the cygdrive prefix.
+    However, the cygdrive prefix can be changed by the user, so symbolic links
+    created using the cygdrive prefix are not foolproof.  With
+    <literal>-U</literal> cygpath will generate such paths prepended by the
+    virtual <pathname>/proc/cygdrive</pathname> symbolic link, which will
+    never change, so the created path is safe against changing the cygdrive
+    prefix.</para>
+
     <para>The <literal>-C</literal> option takes a single parameter:</para>
     <itemizedlist spacing="compact">
       <listitem>