git-reset.txt: render tables correctly under Asciidoctor

Asciidoctor removes the indentation of each line in these tables, so the
last lines of each table have a completely broken alignment.

Similar to 37980505 ("Documentation: render revisions correctly under
Asciidoctor", 2018-05-06), use an explicit literal block to indicate
that we want to keep the leading whitespace in the tables.

Because this gives us some extra indentation, we can remove the one that
we have been carrying explicitly. That is, drop the first six spaces of
indentation on each line. With Asciidoc (8.6.10), this results in
identical rendering before and after this commit, both for git-reset.1
and git-reset.html.

Reported-by: Paweł Samoraj <samoraj.pawel@gmail.com>
Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-reset.txt

@@ -362,53 +362,65 @@ index in state B.  It resets (i.e. moves) the HEAD (i.e. the tip of
 the current branch, if you are on one) to "target" (which has the file
 in state D).
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       A       B     C    D     --soft   A       B     D
-				--mixed  A       D     D
-				--hard   D       D     D
-				--merge (disallowed)
-				--keep  (disallowed)
-
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       A       B     C    C     --soft   A       B     C
-				--mixed  A       C     C
-				--hard   C       C     C
-				--merge (disallowed)
-				--keep   A       C     C
-
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       B       B     C    D     --soft   B       B     D
-				--mixed  B       D     D
-				--hard   D       D     D
-				--merge  D       D     D
-				--keep  (disallowed)
-
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       B       B     C    C     --soft   B       B     C
-				--mixed  B       C     C
-				--hard   C       C     C
-				--merge  C       C     C
-				--keep   B       C     C
-
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       B       C     C    D     --soft   B       C     D
-				--mixed  B       D     D
-				--hard   D       D     D
-				--merge (disallowed)
-				--keep  (disallowed)
-
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       B       C     C    C     --soft   B       C     C
-				--mixed  B       C     C
-				--hard   C       C     C
-				--merge  B       C     C
-				--keep   B       C     C
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ A       B     C    D     --soft   A       B     D
+			  --mixed  A       D     D
+			  --hard   D       D     D
+			  --merge (disallowed)
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ A       B     C    C     --soft   A       B     C
+			  --mixed  A       C     C
+			  --hard   C       C     C
+			  --merge (disallowed)
+			  --keep   A       C     C
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       B     C    D     --soft   B       B     D
+			  --mixed  B       D     D
+			  --hard   D       D     D
+			  --merge  D       D     D
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       B     C    C     --soft   B       B     C
+			  --mixed  B       C     C
+			  --hard   C       C     C
+			  --merge  C       C     C
+			  --keep   B       C     C
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       C     C    D     --soft   B       C     D
+			  --mixed  B       D     D
+			  --hard   D       D     D
+			  --merge (disallowed)
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       C     C    C     --soft   B       C     C
+			  --mixed  B       C     C
+			  --hard   C       C     C
+			  --merge  B       C     C
+			  --keep   B       C     C
+....
 "reset --merge" is meant to be used when resetting out of a conflicted
 merge. Any mergy operation guarantees that the working tree file that is
@@ -431,21 +443,25 @@ entries.
 The following tables show what happens when there are unmerged
 entries:
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       X       U     A    B     --soft  (disallowed)
-				--mixed  X       B     B
-				--hard   B       B     B
-				--merge  B       B     B
-				--keep  (disallowed)
-
-      working index HEAD target         working index HEAD
-      ----------------------------------------------------
-       X       U     A    A     --soft  (disallowed)
-				--mixed  X       A     A
-				--hard   A       A     A
-				--merge  A       A     A
-				--keep  (disallowed)
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ X       U     A    B     --soft  (disallowed)
+			  --mixed  X       B     B
+			  --hard   B       B     B
+			  --merge  B       B     B
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ X       U     A    A     --soft  (disallowed)
+			  --mixed  X       A     A
+			  --hard   A       A     A
+			  --merge  A       A     A
+			  --keep  (disallowed)
+....
 X means any state and U means an unmerged index.