diff, log doc: small grammer, format, and language fixes

- Replace "SHA-1" by "object name", the modern name for hashes.

- Correct a few grammar weaknesses.

- Do not accidentally format a phrase in teletype font where quotes are
  intended.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/diff-generate-patch.txt

@@ -53,7 +53,7 @@ similarity index value of 100% is thus reserved for two equal
 files, while 100% dissimilarity means that no line from the old
 file made it into the new one.
 +
-The index line includes the SHA-1 checksum before and after the change.
+The index line includes the blob object names before and after the change.
 The <mode> is included if the file mode does not change; otherwise,
 separate lines indicate the old and the new mode.
 
@@ -74,7 +74,7 @@ separate lines indicate the old and the new mode.
       rename to a
 
 
-combined diff format
+Combined diff format
 --------------------
 
 Any diff-generating command can take the `-c` or `--cc` option to
@@ -84,7 +84,7 @@ linkgit:git-show[1]. Note also that you can give the `-m` option to any
 of these commands to force generation of diffs with individual parents
 of a merge.
 
-A 'combined diff' format looks like this:
+A "combined diff" format looks like this:
 
 ------------
 diff --combined describe.c
@@ -117,11 +117,11 @@ index fabadb8,cc95eb0..4866510
 ------------
 
 1.   It is preceded with a "git diff" header, that looks like
-     this (when `-c` option is used):
+     this (when the `-c` option is used):
 
        diff --combined file
 +
-or like this (when `--cc` option is used):
+or like this (when the `--cc` option is used):
 
        diff --cc file
 
@@ -164,7 +164,7 @@ parents.
 4.   Chunk header format is modified to prevent people from
      accidentally feeding it to `patch -p1`. Combined diff format
      was created for review of merge commit changes, and was not
-     meant for apply. The change is similar to the change in the
+     meant to be applied. The change is similar to the change in the
      extended 'index' header:
 
        @@@ <from-file-range> <from-file-range> <to-file-range> @@@