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[PATCH v2 1/9] fetch: optionally allow disabling FETCH_HEAD update

From
Junio C Hamano via GitGitGadget <gitgitgadget@gmail.com>
Date
Aug 18, 2020, 14:25 UTC
Message-ID
<f3bc0b2d921a88e4a19f80645cfac5c5039a0450.1597760730.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.696.v2.git.1597760730.gitgitgadget@gmail.com>
From: Junio C Hamano <gitster@pobox.com>

If you run fetch but record the result in remote-tracking branches, and either if you do nothing with the fetched refs (e.g. you are merely mirroring) or if you always work from the remote-tracking refs (e.g. you fetch and then merge origin/branchname separately), you can get away with having no FETCH_HEAD at all.

Teach "git fetch" a command line option "--[no-]write-fetch-head". The default is to write FETCH_HEAD, and the option is primarily meant to be used with the "--no-" prefix to override this default, because there is no matching fetch.writeFetchHEAD configuration variable to flip the default to off (in which case, the positive form may become necessary to defeat it).

Note that under "--dry-run" mode, FETCH_HEAD is never written; otherwise you'd see list of objects in the file that you do not actually have. Passing `--write-fetch-head` does not force `git fetch` to write the file.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/fetch-options.txt |  9 +++++++++
 builtin/fetch.c                 | 15 ++++++++++++---
 t/t5510-fetch.sh                | 15 +++++++++++++--
 t/t5521-pull-options.sh         |  7 +++++++
 4 files changed, 41 insertions(+), 5 deletions(-)
diff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt
index 495bc8ab5a..b65a758661 100644
--- a/Documentation/fetch-options.txt
+++ b/Documentation/fetch-options.txt
@@ -64,6 +64,15 @@ documented in linkgit:git-config[1].
 --dry-run::
 	Show what would be done, without making any changes.
 
+ifndef::git-pull[]
+--[no-]write-fetch-head::
+	Write the list of remote refs fetched in the `FETCH_HEAD`
+	file directly under `$GIT_DIR`.  This is the default.
+	Passing `--no-write-fetch-head` from the command line tells
+	Git not to write the file.  Under `--dry-run` option, the
+	file is never written.
+endif::git-pull[]
+
 -f::
 --force::
 	When 'git fetch' is used with `<src>:<dst>` refspec it may
diff --git a/builtin/fetch.c b/builtin/fetch.c
index c8b9366d3c..cb38e6f5ec 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -56,6 +56,7 @@ static int prune_tags = -1; /* unspecified */
 #define PRUNE_TAGS_BY_DEFAULT 0 /* do we prune tags by default? */
 
 static int all, append, dry_run, force, keep, multiple, update_head_ok;
+static int write_fetch_head = 1;
 static int verbosity, deepen_relative, set_upstream;
 static int progress = -1;
 static int enable_auto_gc = 1;
@@ -162,6 +163,8 @@ static struct option builtin_fetch_options[] = {
 		    PARSE_OPT_OPTARG, option_fetch_parse_recurse_submodules),
 	OPT_BOOL(0, "dry-run", &dry_run,
 		 N_("dry run")),
+	OPT_BOOL(0, "write-fetch-head", &write_fetch_head,
+		 N_("write fetched references to the FETCH_HEAD file")),
 	OPT_BOOL('k', "keep", &keep, N_("keep downloaded pack")),
 	OPT_BOOL('u', "update-head-ok", &update_head_ok,
 		    N_("allow updating of HEAD ref")),
@@ -895,7 +898,9 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 	const char *what, *kind;
 	struct ref *rm;
 	char *url;
-	const char *filename = dry_run ? "/dev/null" : git_path_fetch_head(the_repository);
+	const char *filename = (!write_fetch_head
+				? "/dev/null"
+				: git_path_fetch_head(the_repository));
 	int want_status;
 	int summary_width = transport_summary_width(ref_map);
 
@@ -1329,7 +1334,7 @@ static int do_fetch(struct transport *transport,
 	}
 
 	/* if not appending, truncate FETCH_HEAD */
-	if (!append && !dry_run) {
+	if (!append && write_fetch_head) {
 		retcode = truncate_fetch_head();
 		if (retcode)
 			goto cleanup;
@@ -1596,7 +1601,7 @@ static int fetch_multiple(struct string_list *list, int max_children)
 	int i, result = 0;
 	struct strvec argv = STRVEC_INIT;
 
-	if (!append && !dry_run) {
+	if (!append && write_fetch_head) {
 		int errcode = truncate_fetch_head();
 		if (errcode)
 			return errcode;
@@ -1797,6 +1802,10 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 	if (depth || deepen_since || deepen_not.nr)
 		deepen = 1;
 
+	/* FETCH_HEAD never gets updated in --dry-run mode */
+	if (dry_run)
+		write_fetch_head = 0;
+
 	if (all) {
 		if (argc == 1)
 			die(_("fetch --all does not take a repository argument"));
diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh
index 9850ecde5d..5bd1f953af 100755
--- a/t/t5510-fetch.sh
+++ b/t/t5510-fetch.sh
@@ -539,13 +539,24 @@ test_expect_success 'fetch into the current branch with --update-head-ok' '
 
 '
 
-test_expect_success 'fetch --dry-run' '
-
+test_expect_success 'fetch --dry-run does not touch FETCH_HEAD' '
 	rm -f .git/FETCH_HEAD &&
 	git fetch --dry-run . &&
 	! test -f .git/FETCH_HEAD
 '
 
+test_expect_success '--no-write-fetch-head does not touch FETCH_HEAD' '
+	rm -f .git/FETCH_HEAD &&
+	git fetch --no-write-fetch-head . &&
+	! test -f .git/FETCH_HEAD
+'
+
+test_expect_success '--write-fetch-head gets defeated by --dry-run' '
+	rm -f .git/FETCH_HEAD &&
+	git fetch --dry-run --write-fetch-head . &&
+	! test -f .git/FETCH_HEAD
+'
+
 test_expect_success "should be able to fetch with duplicate refspecs" '
 	mkdir dups &&
 	(
diff --git a/t/t5521-pull-options.sh b/t/t5521-pull-options.sh
index 159afa7ac8..db1a381cd9 100755
--- a/t/t5521-pull-options.sh
+++ b/t/t5521-pull-options.sh
@@ -85,6 +85,13 @@ test_expect_success 'git pull --cleanup errors early on invalid argument' '
 	test -s err)
 '
 
+test_expect_success 'git pull --no-write-fetch-head fails' '
+	mkdir clonedwfh &&
+	(cd clonedwfh && git init &&
+	test_expect_code 129 git pull --no-write-fetch-head "../parent" >out 2>err &&
+	test_must_be_empty out &&
+	test_i18ngrep "no-write-fetch-head" err)
+'
 
 test_expect_success 'git pull --force' '
 	mkdir clonedoldstyle &&
-- 
gitgitgadget
Previous: Derrick Stolee via GitGitGadgetNext: Derrick Stolee via GitGitGadget
Message 24 of 66 in “Maintenance II: prefetch, loose-objects, incremental-repack tasks”
  1. 0/9 Maintenance II: prefetch, loose-objects, incremental-repack tasksDerrick Stolee via GitGitGadget, Aug 6, 2020
  2. 8/9 maintenance: auto-size incremental-repack batchDerrick Stolee via GitGitGadget, Aug 6, 2020
  3. Son Luong NgocAug 6, 2020
  4. Derrick StoleeAug 6, 2020
  5. 6/9 midx: use start_delayed_progress()Derrick Stolee via GitGitGadget, Aug 6, 2020
  6. 9/9 maintenance: add incremental-repack auto conditionDerrick Stolee via GitGitGadget, Aug 6, 2020
  7. 7/9 maintenance: add incremental-repack taskDerrick Stolee via GitGitGadget, Aug 6, 2020
  8. 5/9 midx: enable core.multiPackIndex by defaultDerrick Stolee via GitGitGadget, Aug 6, 2020
  9. 4/9 maintenance: create auto condition for loose-objectsDerrick Stolee via GitGitGadget, Aug 6, 2020
  10. 3/9 maintenance: add loose-objects taskDerrick Stolee via GitGitGadget, Aug 6, 2020
  11. Emily ShafferAug 12, 2020
  12. Derrick StoleeAug 14, 2020
  13. 2/9 maintenance: add prefetch taskDerrick Stolee via GitGitGadget, Aug 6, 2020
  14. Emily ShafferAug 12, 2020
  15. Derrick StoleeAug 14, 2020
  16. 1/9 fetch: optionally allow disabling FETCH_HEAD updateJunio C Hamano via GitGitGadget, Aug 6, 2020
  17. Emily ShafferAug 12, 2020
  18. Junio C HamanoAug 13, 2020
  19. Jonathan NiederAug 13, 2020
  20. fetch: optionally allow disabling FETCH_HEAD updateJunio C Hamano, Aug 13, 2020
  21. Derrick StoleeAug 14, 2020
  22. Junio C HamanoAug 14, 2020
  23. 0/9 Maintenance II: prefetch, loose-objects, incremental-repack tasksDerrick Stolee via GitGitGadget, Aug 18, 2020
  24. 1/9 fetch: optionally allow disabling FETCH_HEAD updateJunio C Hamano via GitGitGadget, Aug 18, 2020
  25. 3/9 maintenance: add loose-objects taskDerrick Stolee via GitGitGadget, Aug 18, 2020
  26. 5/9 midx: enable core.multiPackIndex by defaultDerrick Stolee via GitGitGadget, Aug 18, 2020
  27. 2/9 maintenance: add prefetch taskDerrick Stolee via GitGitGadget, Aug 18, 2020
  28. 8/9 maintenance: auto-size incremental-repack batchDerrick Stolee via GitGitGadget, Aug 18, 2020
  29. 9/9 maintenance: add incremental-repack auto conditionDerrick Stolee via GitGitGadget, Aug 18, 2020
  30. 7/9 maintenance: add incremental-repack taskDerrick Stolee via GitGitGadget, Aug 18, 2020
  31. 6/9 midx: use start_delayed_progress()Derrick Stolee via GitGitGadget, Aug 18, 2020
  32. 4/9 maintenance: create auto condition for loose-objectsDerrick Stolee via GitGitGadget, Aug 18, 2020
  33. 0/8 Maintenance II: prefetch, loose-objects, incremental-repack tasksDerrick Stolee via GitGitGadget, Aug 25, 2020
  34. 1/8 maintenance: add prefetch taskDerrick Stolee via GitGitGadget, Aug 25, 2020
  35. Jonathan TanSep 22, 2020
  36. 2/8 maintenance: add loose-objects taskDerrick Stolee via GitGitGadget, Aug 25, 2020
  37. Jonathan TanSep 22, 2020
  38. Derrick StoleeSep 24, 2020
  39. 3/8 maintenance: create auto condition for loose-objectsDerrick Stolee via GitGitGadget, Aug 25, 2020
  40. Jonathan TanSep 22, 2020
  41. Derrick StoleeSep 24, 2020
  42. 4/8 midx: enable core.multiPackIndex by defaultDerrick Stolee via GitGitGadget, Aug 25, 2020
  43. Jonathan TanSep 22, 2020
  44. Derrick StoleeSep 24, 2020
  45. 5/8 midx: use start_delayed_progress()Derrick Stolee via GitGitGadget, Aug 25, 2020
  46. 6/8 maintenance: add incremental-repack taskDerrick Stolee via GitGitGadget, Aug 25, 2020
  47. Jonathan TanSep 22, 2020
  48. Derrick StoleeSep 24, 2020
  49. Jonathan TanSep 24, 2020
  50. 8/8 maintenance: add incremental-repack auto conditionDerrick Stolee via GitGitGadget, Aug 25, 2020
  51. Jonathan TanSep 22, 2020
  52. 7/8 maintenance: auto-size incremental-repack batchDerrick Stolee via GitGitGadget, Aug 25, 2020
  53. Junio C HamanoAug 25, 2020
  54. Son Luong NgocAug 26, 2020
  55. Derrick StoleeAug 26, 2020
  56. 0/8 Maintenance II: prefetch, loose-objects, incremental-repack tasksDerrick Stolee via GitGitGadget, Sep 25, 2020
  57. 1/8 maintenance: add prefetch taskDerrick Stolee via GitGitGadget, Sep 25, 2020
  58. 3/8 maintenance: create auto condition for loose-objectsDerrick Stolee via GitGitGadget, Sep 25, 2020
  59. Junio C HamanoSep 25, 2020
  60. Derrick StoleeSep 25, 2020
  61. 4/8 midx: enable core.multiPackIndex by defaultDerrick Stolee via GitGitGadget, Sep 25, 2020
  62. 2/8 maintenance: add loose-objects taskDerrick Stolee via GitGitGadget, Sep 25, 2020
  63. 5/8 midx: use start_delayed_progress()Derrick Stolee via GitGitGadget, Sep 25, 2020
  64. 7/8 maintenance: auto-size incremental-repack batchDerrick Stolee via GitGitGadget, Sep 25, 2020
  65. 8/8 maintenance: add incremental-repack auto conditionDerrick Stolee via GitGitGadget, Sep 25, 2020
  66. 6/8 maintenance: add incremental-repack taskDerrick Stolee via GitGitGadget, Sep 25, 2020

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