git.txt: correct stale 'GIT_EXTERNAL_DIFF' description

From: Philippe Blain <[email protected]>

In fde97d8ac6 (Update documentation to remove incorrect GIT_DIFF_OPTS example., 2006-11-27), the description of the 'GIT_EXTERNAL_DIFF' variable was moved from 'diff-format.txt' to 'git.txt', and the documentation was updated to remove a 'diff(1)' invocation since Git did not use an external diff program anymore by default.

However, the description of 'GIT_EXTERNAL_DIFF' still mentions "instead of the diff invocation described above", which is confusing.

Correct that outdated sentence.

Also, link to git(1) in 'diff-generate-patch.txt' when GIT_DIFF_OPTS and GIT_EXTERNAL_DIFF are mentioned, so that users can easily know what these variables are about.

---
git.txt: correct stale 'GIT_EXTERNAL_DIFF' description

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-718%2Fphil-blain%2Fgit-external-diff-wording-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-718/phil-blain/git-external-diff-wording-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/718

 Documentation/diff-generate-patch.txt | 3 ++-
 Documentation/git.txt                 | 5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

index e8ed6470fb..b10ff4caa6 100644
@@ -10,7 +10,8 @@ linkgit:git-diff-tree[1], or
 linkgit:git-diff-files[1]
 with the `-p` option produces patch text.
 You can customize the creation of patch text via the
-`GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables.
+`GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables
+(see linkgit:git[1]).
 
 What the -p option produces is slightly different from the traditional
 diff format:

index 2fc92586b5..98bdf0983c 100644
@@ -551,8 +551,9 @@ Git Diffs
 
 `GIT_EXTERNAL_DIFF`::
 	When the environment variable `GIT_EXTERNAL_DIFF` is set, the
-	program named by it is called, instead of the diff invocation
-	described above.  For a path that is added, removed, or modified,
+	program named by it is called to generate diffs, and Git
+	does not use its builtin diff machinery.
+	For a path that is added, removed, or modified,
 	`GIT_EXTERNAL_DIFF` is called with 7 parameters:
 
 	path old-file old-hex old-mode new-file new-hex new-mode

base-commit: d9cd4331470f4d9d78677f12dc79063dab832f53

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