manpages: use teletype font for sample command lines

I think that some of these uses of italics were meant to be
rendered in quotation marks, anyway.

Signed-off-by: Jonathan Nieder <jrnieder@uchicago.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-gui.txt

@@ -71,7 +71,7 @@ git gui citool::
 
 git citool::
 
-	Same as 'git gui citool' (above).
+	Same as `git gui citool` (above).
 
 git gui browser maint::
 

Documentation/git-help.txt

@@ -23,7 +23,7 @@ If a git command is named, a manual page for that command is brought
 up. The 'man' program is used by default for this purpose, but this
 can be overridden by other options or configuration variables.
 
-Note that 'git --help ...' is identical as 'git help ...' because the
+Note that `git --help ...` is identical to `git help ...` because the
 former is internally converted into the latter.
 
 OPTIONS

Documentation/git-reflog.txt

@@ -36,7 +36,7 @@ The subcommand "show" (which is also the default, in the absence of any
 subcommands) will take all the normal log options, and show the log of
 the reference provided in the command-line (or `HEAD`, by default).
 The reflog will cover all recent actions (HEAD reflog records branch switching
-as well).  It is an alias for 'git log -g --abbrev-commit --pretty=oneline';
+as well).  It is an alias for `git log -g --abbrev-commit --pretty=oneline`;
 see linkgit:git-log[1].
 
 The reflog is useful in various git commands, to specify the old value
@@ -46,7 +46,7 @@ point to one week ago", and so on. See linkgit:git-rev-parse[1] for
 more details.
 
 To delete single entries from the reflog, use the subcommand "delete"
-and specify the _exact_ entry (e.g. ``git reflog delete master@\{2\}'').
+and specify the _exact_ entry (e.g. "`git reflog delete master@\{2\}`").
 
 
 OPTIONS

Documentation/git.txt

@@ -136,8 +136,8 @@ OPTIONS
 +
 Other options are available to control how the manual page is
 displayed. See linkgit:git-help[1] for more information,
-because 'git --help ...' is converted internally into 'git
-help ...'.
+because `git --help ...` is converted internally into `git
+help ...`.
 
 --exec-path::
 	Path to wherever your core git programs are installed.

Documentation/gitcore-tutorial.txt

@@ -1655,7 +1655,7 @@ branch before these two merges by resetting it to 'master~2':
 $ git reset --hard master~2
 ------------
 
-You can make sure 'git show-branch' matches the state before
+You can make sure `git show-branch` matches the state before
 those two 'git-merge' you just did.  Then, instead of running
 two 'git-merge' commands in a row, you would merge these two
 branch heads (this is known as 'making an Octopus'):