docs: make notes regarding credential line reading

This commit adds notes to git-credential.txt and to gitcredentials.txt
specifying that 'LF' and 'CR/LF' endings are treated the same.

Documentation/git-credential.txt

@@ -112,7 +112,9 @@ specified by a key-value pair, separated by an `=` (equals) sign,
 followed by a newline. The key may contain any bytes except `=`,
 newline, or NUL. The value may contain any bytes except newline or NUL.
 In both cases, all bytes are treated as-is (i.e., there is no quoting,
-and one cannot transmit a value with newline or NUL in it). The list of
+and one cannot transmit a value with newline or NUL in it). Note that
+Git will treat a carriage return before the final newline as part of
+line ending, and not part of the data. The list of
 attributes is terminated by a blank line or end-of-file.
 Git understands the following attributes:
 

Documentation/gitcredentials.txt

@@ -139,6 +139,8 @@ entry for `https://example.com/bar/baz.git` (in addition to matching the config
 entry for `https://example.com`) but will not match a config entry for
 `https://example.com/bar`.
 
+Note that Git will treat a carriage return before the final newline as part 
+of line ending, and not part of the data.
 
 CONFIGURATION OPTIONS
 ---------------------