Documentation: AsciiDoc spells em-dash as double-dashes, not triple

Again, we do not usually process release notes with AsciiDoc, but it
is better to be consistent.

This incidentally reveals breakages left by an ancient 5e00439
(Documentation: build html for all files in technical and howto,
2012-10-23).  The index-format documentation was originally written
to be read as straight text without formatting and when the commit
forced everything in Documentation/ to go through AsciiDoc, it did
not do any adjustment--hence the double-dashes will be seen in the
resulting text that is rendered as preformatted fixed-width without
converted into em-dashes.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: gitster

Documentation/RelNotes/1.7.7.txt

@@ -84,7 +84,7 @@ Updates since v1.7.6
    logic used by "git diff" to determine the hunk header.
 
  * Invoking the low-level "git http-fetch" without "-a" option (which
-   git itself never did---normal users should not have to worry about
+   git itself never did--normal users should not have to worry about
    this) is now deprecated.
 
  * The "--decorate" option to "git log" and its family learned to

Documentation/RelNotes/1.9.0.txt

@@ -177,7 +177,7 @@ Performance, Internal Implementation, etc.
  * The naming convention of the packfiles has been updated; it used to
    be based on the enumeration of names of the objects that are
    contained in the pack, but now it also depends on how the packed
-   result is represented---packing the same set of objects using
+   result is represented--packing the same set of objects using
    different settings (or delta order) would produce a pack with
    different name.
 

Documentation/git-bisect.txt

@@ -245,7 +245,7 @@ cannot be tested. If the script exits with this code, the current
 revision will be skipped (see `git bisect skip` above). 125 was chosen
 as the highest sensible value to use for this purpose, because 126 and 127
 are used by POSIX shells to signal specific error status (127 is for
-command not found, 126 is for command found but not executable---these
+command not found, 126 is for command found but not executable--these
 details do not matter, as they are normal errors in the script, as far as
 "bisect run" is concerned).
 

Documentation/git-fetch.txt

@@ -71,7 +71,7 @@ This configuration is used in two ways:
 * When `git fetch` is run without specifying what branches
   and/or tags to fetch on the command line, e.g. `git fetch origin`
   or `git fetch`, `remote.<repository>.fetch` values are used as
-  the refspecs---they specify which refs to fetch and which local refs
+  the refspecs--they specify which refs to fetch and which local refs
   to update.  The example above will fetch
   all branches that exist in the `origin` (i.e. any ref that matches
   the left-hand side of the value, `refs/heads/*`) and update the

Documentation/git-push.txt

@@ -61,7 +61,7 @@ be named.
 If `git push [<repository>]` without any `<refspec>` argument is set to
 update some ref at the destination with `<src>` with
 `remote.<repository>.push` configuration variable, `:<dst>` part can
-be omitted---such a push will update a ref that `<src>` normally updates
+be omitted--such a push will update a ref that `<src>` normally updates
 without any `<refspec>` on the command line.  Otherwise, missing
 `:<dst>` means to update the same ref as the `<src>`.
 +

Documentation/technical/index-format.txt

@@ -170,7 +170,7 @@ Git index format
 
   The entries are written out in the top-down, depth-first order.  The
   first entry represents the root level of the repository, followed by the
-  first subtree---let's call this A---of the root level (with its name
+  first subtree--let's call this A--of the root level (with its name
   relative to the root level), followed by the first subtree of A (with
   its name relative to A), ...