[PATCH 1/5] refs: Introduce pseudoref and per-worktree ref concepts

From

David Turner <dturner@twopensource.com>

Date

Jul 27, 2015, 20:08 UTC

Message-ID

<1438027720-23074-2-git-send-email-dturner@twopensource.com>

In-Reply-To

<1438027720-23074-1-git-send-email-dturner@twopensource.com>

Add glossary entries for both concepts.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 Documentation/glossary-content.txt | 21 +++++++++++++++++++++
 refs.c                             | 23 +++++++++++++++++++++++
 refs.h                             |  2 ++
 3 files changed, 46 insertions(+)

diff --git a/Documentation/glossary-content.txt b/Documentation/glossary-content.txt
index ab18f4b..67952f3 100644
--- a/Documentation/glossary-content.txt
+++ b/Documentation/glossary-content.txt
@@ -411,6 +411,27 @@ exclude;;
 	core Git. Porcelains expose more of a <<def_SCM,SCM>>
 	interface than the <<def_plumbing,plumbing>>.
 
+[[def_per_worktree_ref]]per-worktree ref::
+	Refs that are per-<<def_worktree,worktree>>, rather than
+	global.  This is presently only <<def_HEAD,HEAD>>, but might
+	later include other unusual refs.
+
+[[def_pseudoref]]pseudoref::
+	Pseudorefs are a class of files under `$GIT_DIR` which behave
+	like refs for the purposes of rev-parse, but which are treated
+	specially by git.  Psuedorefs both have names are all-caps,
+	and always start with a line consisting of a
+	<<def_sha1,SHA-1>> followed by whitespace.  So, HEAD is not a
+	pseudoref, because it is sometimes a symbolic ref.  They might
+	optionally some additional data.  `MERGE_HEAD` and
+	`CHERRY_PICK_HEAD` are examples.  Unlike
+	<<def_per_worktree_ref,per-worktree refs>>, these files cannot
+	be symbolic refs, and never have reflogs.  They also cannot be
+	updated through the normal ref update machinery.  Instead,
+	they are updated by directly writing to the files.  However,
+	they can be read as if they were refs, so `git rev-parse
+	MERGE_HEAD` will work.
+
 [[def_pull]]pull::
 	Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and
 	<<def_merge,merge>> it.  See also linkgit:git-pull[1].
diff --git a/refs.c b/refs.c
index 0b96ece..0d10b7b 100644
--- a/refs.c
+++ b/refs.c
@@ -2848,6 +2848,29 @@ static int delete_ref_loose(struct ref_lock *lock, int flag, struct strbuf *err)
 	return 0;
 }
 
+int is_per_worktree_ref(const char *refname)
+{
+	return !strcmp(refname, "HEAD");
+}
+
+static int is_pseudoref(const char *refname)
+{
+	const char *c;
+
+	if (strchr(refname, '/'))
+		return 0;
+
+	if (is_per_worktree_ref(refname))
+		return 0;
+
+	for (c = refname; *c; ++c) {
+		if (!isupper(*c) && *c != '-' && *c != '_')
+			return 0;
+	}
+
+	return 1;
+}
+
 int delete_ref(const char *refname, const unsigned char *old_sha1,
 	       unsigned int flags)
 {
diff --git a/refs.h b/refs.h
index e4e46c3..bd5526e 100644
--- a/refs.h
+++ b/refs.h
@@ -445,6 +445,8 @@ extern int parse_hide_refs_config(const char *var, const char *value, const char
 
 extern int ref_is_hidden(const char *);
 
+int is_per_worktree_ref(const char *refname);
+
 enum expire_reflog_flags {
 	EXPIRE_REFLOGS_DRY_RUN = 1 << 0,
 	EXPIRE_REFLOGS_UPDATE_REF = 1 << 1,

-- 
2.0.4.315.gad8727a-twtrsrc