Documentation: fix linkgit references

There are a handful of incorrect "linkgit:<page>[<section>]"
instances in our documentation set.

 * Some have an extra colon after "linkgit:"; fix them by removing
   the extra colon;

 * Some refer to a page outside the Git suite, namely curl(1); fix
   them by using the `curl(1)` that already appears on the same page
   for the same purpose of referring the readers to its manual page.

 * Some spell the name of the page incorrectly, e.g. "rev-list" when
   they mean "git-rev-list"; fix them.

 * Some list the manual section incorrectly; fix them to make sure
   they match what is at the top of the target of the link.

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

Documentation/technical/api-credentials.txt

@@ -243,7 +243,7 @@ appended to its command line, which is one of:
 The details of the credential will be provided on the helper's stdin
 stream. The exact format is the same as the input/output format of the
 `git credential` plumbing command (see the section `INPUT/OUTPUT
-FORMAT` in linkgit:git-credential[7] for a detailed specification).
+FORMAT` in linkgit:git-credential[1] for a detailed specification).
 
 For a `get` operation, the helper should produce a list of attributes
 on stdout in the same format. A helper is free to produce a subset, or
@@ -268,4 +268,4 @@ See also
 
 linkgit:gitcredentials[7]
 
-linkgit:git-config[5] (See configuration variables `credential.*`)
+linkgit:git-config[1] (See configuration variables `credential.*`)